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  • Force external function to be const

    - by vanna
    Here is my problem. I made a class with a member function declared as const that uses an external function that I cannot modify (declared in someone else's code) and that is not declared const. More precisely Someone else's code class B { public: void foo(); }; My code class A : public B { public: void bar() const { this->foo(); } }; I know that for member data we can force const-correctness by using mutable or const_cast. How can I 'hack' foo such that my compiler understands that I would like to use it as if it was const even if it is not declared in someone else's code ?

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  • Modifying a const through a non-const pointer

    - by jasonline
    I'm a bit confused what happened in the following code: const int e = 2; int* w = ( int* ) &e; // (1) cast to remove const-ness *w = 5; // (2) cout << *w << endl; // (3) outputs 5 cout << e << endl; // (4) outputs 2 cout << "w = " << w << endl; // (5) w points to the address of e cout << "&e = " << &e << endl; In (1), w points to the address of e. In (2), that value was changed to 5. However, when the values of *w and e were displayed, their values are different. But if you print value of w pointer and &e, they have the same value/address. How come e still contained 2, even if it was changed to 5? Were they stored in a separate location? Or a temporary? But how come the value pointed by w is still the address of e?

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  • Cast from Void* to TYPE* using C++ style cast: static_cast or reinterpret_cast

    - by David Relihan
    So if your converting from Void* to Type* or from Type* to Void* should you use: void func(void *p) { Params *params = static_cast<Params*>(p); } or void func(void *p) { Params *params = reinterpret_cast<Params*>(p); } To me static_cast seems the more correct but I've seen both used for the same purpose. Also, does the direction of the conversion matter. i.e. should I still use static_cast for: _beginthread(func,0,static_cast<void*>(params) I have read the other questions on C++ style casting but I'm still not sure what the correct way is for this scenario (I think it is static_cast)

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  • Implicit conversion : const reference vs non-const reference vs non-reference

    - by Nawaz
    Consider this code, struct A {}; struct B { B(const A&) {} }; void f(B) { cout << "f()"<<endl; } void g(A &a) { cout << "g()" <<endl; f(a); //a is implicitly converted into B. } int main() { A a; g(a); } This compiles fine, runs fine. But if I change f(B) to f(B&), it doesn't compile. If I write f(const B&), it again compiles fine, runs fine. Why is the reason and rationale? Summary: void f(B); //okay void f(B&); //error void f(const B&); //okay I would like to hear reasons, rationale and reference(s) from the language specification, for each of these cases. Of course, the function signatures themselves are not incorrect. Rather A implicitly converts into B and const B&, but not into B&, and that causes the compilation error.

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  • Double pointer const-correctness warnings in C

    - by Michael Koval
    You can obviously cast a pointer to non-const data to a a pointer of the same type to const data: int *x = NULL; int const *y = x; Adding additional const qualifiers to match the additional indirection should logically work the same way: int * *x = NULL; int *const *y = x; /* okay */ int const *const *z = y; /* warning */ Compiling this with GCC or Clang with the -Wall flag, however, results in the following warning: test.c:4:23: warning: initializing 'int const *const *' with an expression of type 'int *const *' discards qualifiers in nested pointer types int const *const *z = y; /* warning */ ^ ~ Why does adding an additional const qualifier "discard qualifiers in nested pointer types"?

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  • Trying to install realtek drivers for ASUS USB-N13, encountering "Compile make driver error: 2"

    - by limp_chimp
    I'm trying to put an ASUS USB-N13 wireless adapter in my desktop running Ubuntu 12.04. The details of my problem are identical to the one described in this question: Connecting Asus USB-N13 Wireless Adapter. As such, I'm running through the exact steps laid out in the top-rated answer to that question. All was going well until I get to building the drivers. sudo bash install.sh produces the following output: ################################################## Realtek Wi-Fi driver Auto installation script Novembor, 21 2011 v1.1.0 ################################################## Decompress the driver source tar ball: rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405.tar.gz rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/autoconf_rtl8712_usb_linux.h rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/clean rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl8712_cmd.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/config rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/crypto/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/crypto/rtl871x_security.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/debug/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/debug/rtl871x_debug.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/eeprom/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/eeprom/rtl871x_eeprom.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/efuse/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/efuse/rtl8712_efuse.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/hal/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/hal/rtl8712/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/hal/rtl8712/hal_init.c [...truncated for space...] rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/ioctl/rtl871x_ioctl_linux.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/ioctl/rtl871x_ioctl_query.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/ioctl/rtl871x_ioctl_rtl.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/ioctl/rtl871x_ioctl_set.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/Kconfig rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/led/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/led/rtl8712_led.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/Makefile rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/mlme/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/mlme/ieee80211.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/mlme/rtl871x_mlme.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/mp/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/mp/rtl871x_mp.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/mp/rtl871x_mp_ioctl.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/linux/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/linux/cmd_linux.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/linux/ioctl_cfg80211.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/linux/io_linux.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/linux/mlme_linux.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/linux/recv_linux.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/linux/rtw_android.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_dep/linux/xmit_linux.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_intf/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_intf/linux/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_intf/linux/os_intfs.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_intf/linux/usb_intf.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/os_intf/osdep_service.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/pwrctrl/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/pwrctrl/rtl871x_pwrctrl.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/recv/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/recv/rtl8712_recv.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/recv/rtl871x_recv.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/rf/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/rf/rtl8712_rf.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/rf/rtl871x_rf.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/runwpa rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/sta_mgt/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/sta_mgt/rtl871x_sta_mgt.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/wlan0dhcp rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/wpa1.conf rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/xmit/ rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/xmit/rtl8712_xmit.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/xmit/rtl871x_xmit.c rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405 Authentication requested [root] for make clean: rm -fr *.mod.c *.mod *.o .*.cmd *.ko *~ rm .tmp_versions -fr ; rm Module.symvers -fr cd cmd ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd crypto ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd debug ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd eeprom ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd hal/rtl8712 ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd io ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd ioctl ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd led ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd mlme ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd mp ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd os_dep/linux ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd os_intf ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd os_intf/linux ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd pwrctrl ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd recv ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd rf ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd sta_mgt ; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd xmit; rm -fr *.mod.c *.mod *.o .*.cmd *.ko cd efuse; rm -fr *.mod.c *.mod *.o .*.cmd *.ko Authentication requested [root] for make driver: make ARCH=x86_64 CROSS_COMPILE= -C /lib/modules/3.2.0-23-generic/build M=/home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405 modules make[1]: Entering directory `/usr/src/linux-headers-3.2.0-23-generic' CC [M] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.o In file included from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:23:0: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/osdep_service.h: In function ‘_init_timer’: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/osdep_service.h:151:17: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] In file included from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/rtl871x_ht.h:25:0, from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/drv_types.h:67, from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:24: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h: In function ‘get_da’: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:350:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:350:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:353:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:353:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:356:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:356:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:359:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:359:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h: In function ‘get_sa’: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:374:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:374:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:377:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:377:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:380:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:380:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:383:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:383:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h: In function ‘get_hdr_bssid’: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:397:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:397:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:400:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:400:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:403:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/wifi.h:403:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] In file included from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/drv_types.h:70:0, from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:24: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/rtl871x_cmd.h: At top level: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/rtl871x_cmd.h:107:25: error: field ‘event_tasklet’ has incomplete type In file included from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/drv_types.h:72:0, from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:24: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/rtl871x_xmit.h:355:24: error: field ‘xmit_tasklet’ has incomplete type In file included from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/drv_types.h:73:0, from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:24: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/rtl871x_recv.h:205:24: error: field ‘recv_tasklet’ has incomplete type In file included from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/drv_types.h:73:0, from /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:24: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/rtl871x_recv.h: In function ‘rxmem_to_recvframe’: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/rtl871x_recv.h:435:30: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/include/rtl871x_recv.h:435:9: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c: In function ‘_init_cmd_priv’: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:93:75: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:101:60: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c: In function ‘_init_evt_priv’: /home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.c:135:59: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] make[2]: *** [/home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/cmd/rtl871x_cmd.o] Error 1 make[1]: *** [_module_/home/thinkpad20/Downloads/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405/driver/rtl8712_8188_8191_8192SU_usb_linux_v2.6.6.0.20120405] Error 2 make[1]: Leaving directory `/usr/src/linux-headers-3.2.0-23-generic' make: *** [modules] Error 2 ################################################## Compile make driver error: 2 Please check error Mesg ################################################## I'm not a superuser, only a hobbyist. I really just want this to work ~.~ so I can get on with my life. Sigh. Anyway, grumbling aside, I hope people can help.

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  • C#/.NET Little Wonders: Use Cast() and TypeOf() to Change Sequence Type

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. We’ve seen how the Select() extension method lets you project a sequence from one type to a new type which is handy for getting just parts of items, or building new items.  But what happens when the items in the sequence are already the type you want, but the sequence itself is typed to an interface or super-type instead of the sub-type you need? For example, you may have a sequence of Rectangle stored in an IEnumerable<Shape> and want to consider it an IEnumerable<Rectangle> sequence instead.  Today we’ll look at two handy extension methods, Cast<TResult>() and OfType<TResult>() which help you with this task. Cast<TResult>() – Attempt to cast all items to type TResult So, the first thing we can do would be to attempt to create a sequence of TResult from every item in the source sequence.  Typically we’d do this if we had an IEnumerable<T> where we knew that every item was actually a TResult where TResult inherits/implements T. For example, assume the typical Shape example classes: 1: // abstract base class 2: public abstract class Shape { } 3:  4: // a basic rectangle 5: public class Rectangle : Shape 6: { 7: public int Widtgh { get; set; } 8: public int Height { get; set; } 9: } And let’s assume we have a sequence of Shape where every Shape is a Rectangle… 1: var shapes = new List<Shape> 2: { 3: new Rectangle { Width = 3, Height = 5 }, 4: new Rectangle { Width = 10, Height = 13 }, 5: // ... 6: }; To get the sequence of Shape as a sequence of Rectangle, of course, we could use a Select() clause, such as: 1: // select each Shape, cast it to Rectangle 2: var rectangles = shapes 3: .Select(s => (Rectangle)s) 4: .ToList(); But that’s a bit verbose, and fortunately there is already a facility built in and ready to use in the form of the Cast<TResult>() extension method: 1: // cast each item to Rectangle and store in a List<Rectangle> 2: var rectangles = shapes 3: .Cast<Rectangle>() 4: .ToList(); However, we should note that if anything in the list cannot be cast to a Rectangle, you will get an InvalidCastException thrown at runtime.  Thus, if our Shape sequence had a Circle in it, the call to Cast<Rectangle>() would have failed.  As such, you should only do this when you are reasonably sure of what the sequence actually contains (or are willing to handle an exception if you’re wrong). Another handy use of Cast<TResult>() is using it to convert an IEnumerable to an IEnumerable<T>.  If you look at the signature, you’ll see that the Cast<TResult>() extension method actually extends the older, object-based IEnumerable interface instead of the newer, generic IEnumerable<T>.  This is your gateway method for being able to use LINQ on older, non-generic sequences.  For example, consider the following: 1: // the older, non-generic collections are sequence of object 2: var shapes = new ArrayList 3: { 4: new Rectangle { Width = 3, Height = 13 }, 5: new Rectangle { Width = 10, Height = 20 }, 6: // ... 7: }; Since this is an older, object based collection, we cannot use the LINQ extension methods on it directly.  For example, if I wanted to query the Shape sequence for only those Rectangles whose Width is > 5, I can’t do this: 1: // compiler error, Where() operates on IEnumerable<T>, not IEnumerable 2: var bigRectangles = shapes.Where(r => r.Width > 5); However, I can use Cast<Rectangle>() to treat my ArrayList as an IEnumerable<Rectangle> and then do the query! 1: // ah, that’s better! 2: var bigRectangles = shapes.Cast<Rectangle>().Where(r => r.Width > 5); Or, if you prefer, in LINQ query expression syntax: 1: var bigRectangles = from s in shapes.Cast<Rectangle>() 2: where s.Width > 5 3: select s; One quick warning: Cast<TResult>() only attempts to cast, it won’t perform a cast conversion.  That is, consider this: 1: var intList = new List<int> { 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 }; 2:  3: // casting ints to longs, this should work, right? 4: var asLong = intList.Cast<long>().ToList(); Will the code above work?  No, you’ll get a InvalidCastException. Remember that Cast<TResult>() is an extension of IEnumerable, thus it is a sequence of object, which means that it will box every int as an object as it enumerates over it, and there is no cast conversion from object to long, and thus the cast fails.  In other words, a cast from int to long will succeed because there is a conversion from int to long.  But a cast from int to object to long will not, because you can only unbox an item by casting it to its exact type. For more information on why cast-converting boxed values doesn’t work, see this post on The Dangers of Casting Boxed Values (here). OfType<TResult>() – Filter sequence to only items of type TResult So, we’ve seen how we can use Cast<TResult>() to change the type of our sequence, when we expect all the items of the sequence to be of a specific type.  But what do we do when a sequence contains many different types, and we are only concerned with a subset of a given type? For example, what if a sequence of Shape contains Rectangle and Circle instances, and we just want to select all of the Rectangle instances?  Well, let’s say we had this sequence of Shape: 1: var shapes = new List<Shape> 2: { 3: new Rectangle { Width = 3, Height = 5 }, 4: new Rectangle { Width = 10, Height = 13 }, 5: new Circle { Radius = 10 }, 6: new Square { Side = 13 }, 7: // ... 8: }; Well, we could get the rectangles using Select(), like: 1: var onlyRectangles = shapes.Where(s => s is Rectangle).ToList(); But fortunately, an easier way has already been written for us in the form of the OfType<T>() extension method: 1: // returns only a sequence of the shapes that are Rectangles 2: var onlyRectangles = shapes.OfType<Rectangle>().ToList(); Now we have a sequence of only the Rectangles in the original sequence, we can also use this to chain other queries that depend on Rectangles, such as: 1: // select only Rectangles, then filter to only those more than 2: // 5 units wide... 3: var onlyBigRectangles = shapes.OfType<Rectangle>() 4: .Where(r => r.Width > 5) 5: .ToList(); The OfType<Rectangle>() will filter the sequence to only the items that are of type Rectangle (or a subclass of it), and that results in an IEnumerable<Rectangle>, we can then apply the other LINQ extension methods to query that list further. Just as Cast<TResult>() is an extension method on IEnumerable (and not IEnumerable<T>), the same is true for OfType<T>().  This means that you can use OfType<TResult>() on object-based collections as well. For example, given an ArrayList containing Shapes, as below: 1: // object-based collections are a sequence of object 2: var shapes = new ArrayList 3: { 4: new Rectangle { Width = 3, Height = 5 }, 5: new Rectangle { Width = 10, Height = 13 }, 6: new Circle { Radius = 10 }, 7: new Square { Side = 13 }, 8: // ... 9: }; We can use OfType<Rectangle> to filter the sequence to only Rectangle items (and subclasses), and then chain other LINQ expressions, since we will then be of type IEnumerable<Rectangle>: 1: // OfType() converts the sequence of object to a new sequence 2: // containing only Rectangle or sub-types of Rectangle. 3: var onlyBigRectangles = shapes.OfType<Rectangle>() 4: .Where(r => r.Width > 5) 5: .ToList(); Summary So now we’ve seen two different ways to get a sequence of a superclass or interface down to a more specific sequence of a subclass or implementation.  The Cast<TResult>() method casts every item in the source sequence to type TResult, and the OfType<TResult>() method selects only those items in the source sequence that are of type TResult. You can use these to downcast sequences, or adapt older types and sequences that only implement IEnumerable (such as DataTable, ArrayList, etc.). Technorati Tags: C#,CSharp,.NET,LINQ,Little Wonders,TypeOf,Cast,IEnumerable<T>

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  • What is the best Broadphase Interface for moving spheres?

    - by Molmasepic
    As of now I am working on optimizing the performance of the physics and collision, and as of now I am having some slowdowns on my other computers from my main. I have well over 3000 btSphereShape Rigidbodies and 2/3 of them do not move at all, but I am noticing(by the profile below) that collision is taking a bit of time to maneuver. Each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls ms/call ms/call name 10.09 0.65 0.65 SphereTriangleDetector::collide(btVector3 const&, btVector3&, btVector3&, float&, float&, float) 7.61 1.14 0.49 btSphereTriangleCollisionAlgorithm::processCollision(btCollisionObject*, btCollisionObject*, btDispatcherInfo const&, btManifoldResult*) 5.59 1.50 0.36 btConvexTriangleCallback::processTriangle(btVector3*, int, int) 5.43 1.85 0.35 btQuantizedBvh::reportAabbOverlappingNodex(btNodeOverlapCallback*, btVector3 const&, btVector3 const&) const 4.97 2.17 0.32 btBvhTriangleMeshShape::processAllTriangles(btTriangleCallback*, btVector3 const&, btVector3 const&) const::MyNodeOverlapCallback::processNode(int, int) 4.19 2.44 0.27 btSequentialImpulseConstraintSolver::resolveSingleConstraintRowGeneric(btRigidBody&, btRigidBody&, btSolverConstraint const&) 4.04 2.70 0.26 btSequentialImpulseConstraintSolver::resolveSingleConstraintRowLowerLimit(btRigidBody&, btRigidBody&, btSolverConstraint const&) 3.73 2.94 0.24 Ogre::OctreeSceneManager::walkOctree(Ogre::OctreeCamera*, Ogre::RenderQueue*, Ogre::Octree*, Ogre::VisibleObjectsBoundsInfo*, bool, bool) 3.42 3.16 0.22 btTriangleShape::getVertex(int, btVector3&) const 2.48 3.32 0.16 Ogre::Frustum::isVisible(Ogre::AxisAlignedBox const&, Ogre::FrustumPlane*) const 2.33 3.47 0.15 1246357 0.00 0.00 Gorilla::Layer::setVisible(bool) 2.33 3.62 0.15 SphereTriangleDetector::getClosestPoints(btDiscreteCollisionDetectorInterface::ClosestPointInput const&, btDiscreteCollisionDetectorInterface::Result&, btIDebugDraw*, bool) 1.86 3.74 0.12 btCollisionDispatcher::findAlgorithm(btCollisionObject*, btCollisionObject*, btPersistentManifold*) 1.86 3.86 0.12 btSequentialImpulseConstraintSolver::setupContactConstraint(btSolverConstraint&, btCollisionObject*, btCollisionObject*, btManifoldPoint&, btContactSolverInfo const&, btVector3&, float&, float&, btVector3&, btVector3&) 1.71 3.97 0.11 btTriangleShape::getEdge(int, btVector3&, btVector3&) const 1.55 4.07 0.10 _Unwind_SjLj_Register 1.55 4.17 0.10 _Unwind_SjLj_Unregister 1.55 4.27 0.10 Ogre::D3D9HardwareVertexBuffer::updateBufferResources(char const*, Ogre::D3D9HardwareVertexBuffer::BufferResources*) 1.40 4.36 0.09 btManifoldResult::addContactPoint(btVector3 const&, btVector3 const&, float) 1.40 4.45 0.09 btSequentialImpulseConstraintSolver::setupFrictionConstraint(btSolverConstraint&, btVector3 const&, btRigidBody*, btRigidBody*, btManifoldPoint&, btVector3 const&, btVector3 const&, btCollisionObject*, btCollisionObject*, float, float, float) 1.24 4.53 0.08 btSequentialImpulseConstraintSolver::convertContact(btPersistentManifold*, btContactSolverInfo const&) 1.09 4.60 0.07 408760 0.00 0.00 Living::MapHide() 1.09 4.67 0.07 btSphereTriangleCollisionAlgorithm::~btSphereTriangleCollisionAlgorithm() 1.09 4.74 0.07 inflate_fast EDIT: Updated to show current Profile. I have only listed the functions using over 1% time from the many functions that are being used. Another thing is that each monster has a certain area that they stay in and are only active when a player is in said area. I was wondering if maybe there is a way to deactivate the non-active monsters from bullet(reactivating once in the area again) or maybe theres a different broadphase interface that I should use. The current BPI is btDbvtBroadphase. EDIT: Here is the Profile on the other computer(the top one is my main) Each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls ms/call ms/call name 12.18 1.19 1.19 SphereTriangleDetector::collide(btVector3 const&, btVector3&, btVector3&, float&, float&, float) 6.76 1.85 0.66 btSphereTriangleCollisionAlgorithm::processCollision(btCollisionObject*, btCollisionObject*, btDispatcherInfo const&, btManifoldResult*) 5.83 2.42 0.57 btQuantizedBvh::reportAabbOverlappingNodex(btNodeOverlapCallback*, btVector3 const&, btVector3 const&) const 5.12 2.92 0.50 btConvexTriangleCallback::processTriangle(btVector3*, int, int) 4.61 3.37 0.45 btTriangleShape::getVertex(int, btVector3&) const 4.09 3.77 0.40 _Unwind_SjLj_Register 3.48 4.11 0.34 btBvhTriangleMeshShape::processAllTriangles(btTriangleCallback*, btVector3 const&, btVector3 const&) const::MyNodeOverlapCallback::processNode(int, int) 2.46 4.35 0.24 btSequentialImpulseConstraintSolver::resolveSingleConstraintRowLowerLimit(btRigidBody&, btRigidBody&, btSolverConstraint const&) 2.15 4.56 0.21 _Unwind_SjLj_Unregister 2.15 4.77 0.21 SphereTriangleDetector::getClosestPoints(btDiscreteCollisionDetectorInterface::ClosestPointInput const&, btDiscreteCollisionDetectorInterface::Result&, btIDebugDraw*, bool) 1.84 4.95 0.18 btTriangleShape::getEdge(int, btVector3&, btVector3&) const 1.64 5.11 0.16 btSequentialImpulseConstraintSolver::resolveSingleConstraintRowGeneric(btRigidBody&, btRigidBody&, btSolverConstraint const&) 1.54 5.26 0.15 btSequentialImpulseConstraintSolver::setupContactConstraint(btSolverConstraint&, btCollisionObject*, btCollisionObject*, btManifoldPoint&, btContactSolverInfo const&, btVector3&, float&, float&, btVector3&, btVector3&) 1.43 5.40 0.14 Ogre::D3D9HardwareVertexBuffer::updateBufferResources(char const*, Ogre::D3D9HardwareVertexBuffer::BufferResources*) 1.33 5.53 0.13 btManifoldResult::addContactPoint(btVector3 const&, btVector3 const&, float) 1.13 5.64 0.11 btRigidBody::predictIntegratedTransform(float, btTransform&) 1.13 5.75 0.11 btTriangleIndexVertexArray::getLockedReadOnlyVertexIndexBase(unsigned char const**, int&, PHY_ScalarType&, int&, unsigned char const**, int&, int&, PHY_ScalarType&, int) const 1.02 5.85 0.10 btSphereTriangleCollisionAlgorithm::CreateFunc::CreateCollisionAlgorithm(btCollisionAlgorithmConstructionInfo&, btCollisionObject*, btCollisionObject*) 1.02 5.95 0.10 btSphereTriangleCollisionAlgorithm::btSphereTriangleCollisionAlgorithm(btPersistentManifold*, btCollisionAlgorithmConstructionInfo const&, btCollisionObject*, btCollisionObject*, bool) Edited same as other Profile.

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  • Get non-overlapping dates ranges for prices history data

    - by Anonymouse
    Hello, Let's assume that I have the following table: CREATE TABLE [dbo].[PricesHist]( [Product] varchar NOT NULL, [Price] [float] NOT NULL, [StartDate] [datetime] NOT NULL, [EndDate] [datetime] NOT NULL ) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D2C00000000 AS DateTime), CAST(0x00009D2C00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D2D00000000 AS DateTime), CAST(0x00009D2D00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 2.5, CAST(0x00009D2E00000000 AS DateTime), CAST(0x00009D2E00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3000000000 AS DateTime), CAST(0x00009D3000000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3100000000 AS DateTime), CAST(0x00009D3100000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3400000000 AS DateTime), CAST(0x00009D3400000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 2.5, CAST(0x00009D3500000000 AS DateTime), CAST(0x00009D3500000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3600000000 AS DateTime), CAST(0x00009D3600000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3700000000 AS DateTime), CAST(0x00009D3700000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3800000000 AS DateTime), CAST(0x00009D3800000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3A00000000 AS DateTime), CAST(0x00009D3A00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3B00000000 AS DateTime), CAST(0x00009D3B00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 2.5, CAST(0x00009D3C00000000 AS DateTime), CAST(0x00009D3C00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3D00000000 AS DateTime), CAST(0x00009D3D00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3E00000000 AS DateTime), CAST(0x00009D3E00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D3F00000000 AS DateTime), CAST(0x00009D3F00000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D4100000000 AS DateTime), CAST(0x00009D4100000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D4200000000 AS DateTime), CAST(0x00009D4200000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 2.5, CAST(0x00009D4300000000 AS DateTime), CAST(0x00009D4300000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D4400000000 AS DateTime), CAST(0x00009D4400000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D4500000000 AS DateTime), CAST(0x00009D4500000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D4600000000 AS DateTime), CAST(0x00009D4600000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 4.9, CAST(0x00009D4800000000 AS DateTime), CAST(0x00009D4800000000 AS DateTime)) INSERT [dbo].[PricesHist] ([Product], [Price], [StartDate], [EndDate]) VALUES (N'Apples', 2.5, CAST(0x00009D4A00000000 AS DateTime), CAST(0x00009D4A00000000 AS DateTime)) As you can see, there are two prices on that month for Apples. 4.90 and 2.50. In order to tidy this table up, I need to get this information as a date range rather than a row per day as it currently is. I can obviously do this with Min and Max aggregates easily but the ranges overlap and other business code expect non-overlapping ranges. I also tried to achieve this with self joins and row_number(), but without much success... Here is what I'm trying to achieve as the output: Product | StartDate | EndDate | Price ------------------------------------------- Apples | 01 Mar 2010 | 02 Mar 2010 | 4.90 Apples | 03 Mar 2010 | 03 Mar 2010 | 2.50 Apples | 05 Mar 2010 | 09 Mar 2010 | 4.90 Apples | 10 Mar 2010 | 10 Mar 2010 | 2.50 Apples | 11 Mar 2010 | 16 Mar 2010 | 4.90 Apples | 17 Mar 2010 | 17 Mar 2010 | 2.50 Apples | 18 Mar 2010 | 23 Mar 2010 | 4.90 Apples | 24 Mar 2010 | 24 Mar 2010 | 2.50 Apples | 25 Mar 2010 | 30 Mar 2010 | 4.90 Apples | 31 Mar 2010 | 31 Mar 2010 | 2.50 What would please be the best approach to get this done? Thanks a lot in advance,

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  • Trouble with a query

    - by Mark Allison
    Hi there, I'm having trouble with a query in SQL Server 2008 on some forex trading data. I have a trades table and an orders table. A trade needs to comprise of 2 or more orders. DDL schema and sample data below. What I want to do is write a query that shows the profit/loss in pips for each trade. A pip is 1/1000th of a currency. So the difference between USD 1.3441 and 1.3442 is 1 pip in forex-speak. A trade usually has one entry order and multiple exit orders. So for example if I buy 3 lots of the currency pair GBP/USD at the exchange rate of 1.6100 and then sell 1 lot at 1.6150, 1 lot at 1.6200 and 1 lot at 1.6250 then the profit is (1.6150 - 1.6100) + (1.6200 - 1.6100) + (1.6250 - 1.6100), or 50 + 100 + 150 = 300 pips profit. The trade could also go the other way (Shorting). For example the currency pair can be sold first before it's bought back later at a cheaper price. I would like a query that returns the following: tradeId, currencyPair, profitInPips It seems like a pretty straightforward query, but it's eluding me right now. Here's my DDL and sample data: CREATE TABLE [dbo].[trades]( [tradeId] [int] IDENTITY(1,1) NOT NULL, [currencyPair] [char](6) NOT NULL, CONSTRAINT [PK_trades] PRIMARY KEY CLUSTERED ( [tradeId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO SET ANSI_PADDING OFF GO SET IDENTITY_INSERT [dbo].[trades] ON INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (1, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (2, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (3, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (4, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (5, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (6, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (7, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (8, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (9, N'GBPUSD') INSERT [dbo].[trades] ([tradeId], [currencyPair]) VALUES (10, N'GBPUSD') SET IDENTITY_INSERT [dbo].[trades] OFF GO CREATE TABLE [dbo].[orders]( [orderId] [int] IDENTITY(1,1) NOT NULL, [tradeId] [int] NOT NULL, [amount] [decimal](18, 1) NOT NULL, [buySell] [char](1) NOT NULL, [rate] [decimal](18, 6) NOT NULL, [orderDateTime] [datetime] NOT NULL, CONSTRAINT [PK_orders] PRIMARY KEY CLUSTERED ( [orderId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO SET ANSI_PADDING OFF GO SET IDENTITY_INSERT [dbo].[orders] ON INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (1, 1, CAST(3.0 AS Decimal(18, 1)), N'S', CAST(1.606500 AS Decimal(18, 6)), CAST(0x00009CF40083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (2, 1, CAST(3.0 AS Decimal(18, 1)), N'B', CAST(1.615500 AS Decimal(18, 6)), CAST(0x00009CF400A4CB80 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (3, 2, CAST(3.0 AS Decimal(18, 1)), N'S', CAST(1.608000 AS Decimal(18, 6)), CAST(0x00009CF500000000 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (4, 2, CAST(1.0 AS Decimal(18, 1)), N'B', CAST(1.603000 AS Decimal(18, 6)), CAST(0x00009CF50083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (5, 2, CAST(2.0 AS Decimal(18, 1)), N'B', CAST(1.605500 AS Decimal(18, 6)), CAST(0x00009CF50107AC00 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (6, 3, CAST(3.0 AS Decimal(18, 1)), N'S', CAST(1.595500 AS Decimal(18, 6)), CAST(0x00009CF70083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (7, 3, CAST(1.0 AS Decimal(18, 1)), N'B', CAST(1.590500 AS Decimal(18, 6)), CAST(0x00009CF700C5C100 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (8, 3, CAST(2.0 AS Decimal(18, 1)), N'B', CAST(1.594500 AS Decimal(18, 6)), CAST(0x00009CF701499700 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (9, 4, CAST(3.0 AS Decimal(18, 1)), N'B', CAST(1.611000 AS Decimal(18, 6)), CAST(0x00009CFB0083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (10, 4, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.616000 AS Decimal(18, 6)), CAST(0x00009CFB00A4CB80 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (11, 4, CAST(2.0 AS Decimal(18, 1)), N'S', CAST(1.611500 AS Decimal(18, 6)), CAST(0x00009CFB0107AC00 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (12, 5, CAST(3.0 AS Decimal(18, 1)), N'B', CAST(1.613000 AS Decimal(18, 6)), CAST(0x00009CFC0083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (13, 5, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.618000 AS Decimal(18, 6)), CAST(0x00009CFC0107AC00 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (14, 5, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.623000 AS Decimal(18, 6)), CAST(0x00009CFC0083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (15, 5, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.628000 AS Decimal(18, 6)), CAST(0x00009CFD00C5C100 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (16, 6, CAST(3.0 AS Decimal(18, 1)), N'B', CAST(1.632000 AS Decimal(18, 6)), CAST(0x00009D020083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (17, 6, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.637000 AS Decimal(18, 6)), CAST(0x00009D0200A4CB80 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (18, 6, CAST(2.0 AS Decimal(18, 1)), N'S', CAST(1.630000 AS Decimal(18, 6)), CAST(0x00009D0200C5C100 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (19, 7, CAST(3.0 AS Decimal(18, 1)), N'B', CAST(1.634500 AS Decimal(18, 6)), CAST(0x00009D0201499700 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (20, 7, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.639500 AS Decimal(18, 6)), CAST(0x00009D0300000000 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (21, 7, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.644500 AS Decimal(18, 6)), CAST(0x00009D030083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (22, 7, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.637500 AS Decimal(18, 6)), CAST(0x00009D0300C5C100 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (23, 8, CAST(3.0 AS Decimal(18, 1)), N'S', CAST(1.625000 AS Decimal(18, 6)), CAST(0x00009D0400C5C100 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (24, 8, CAST(1.0 AS Decimal(18, 1)), N'B', CAST(1.620000 AS Decimal(18, 6)), CAST(0x00009D050083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (25, 8, CAST(1.0 AS Decimal(18, 1)), N'B', CAST(1.615000 AS Decimal(18, 6)), CAST(0x00009D0500A4CB80 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (26, 8, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.623000 AS Decimal(18, 6)), CAST(0x00009D050107AC00 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (27, 9, CAST(3.0 AS Decimal(18, 1)), N'S', CAST(1.618000 AS Decimal(18, 6)), CAST(0x00009D0600C5C100 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (28, 9, CAST(1.0 AS Decimal(18, 1)), N'B', CAST(1.613000 AS Decimal(18, 6)), CAST(0x00009D0600D63BC0 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (29, 9, CAST(1.0 AS Decimal(18, 1)), N'B', CAST(1.608000 AS Decimal(18, 6)), CAST(0x00009D0600E6B680 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (30, 9, CAST(1.0 AS Decimal(18, 1)), N'B', CAST(1.613300 AS Decimal(18, 6)), CAST(0x00009D0601391C40 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (31, 10, CAST(3.0 AS Decimal(18, 1)), N'B', CAST(1.614500 AS Decimal(18, 6)), CAST(0x00009D090083D600 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (32, 10, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.619500 AS Decimal(18, 6)), CAST(0x00009D090107AC00 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (33, 10, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.624500 AS Decimal(18, 6)), CAST(0x00009D0901499700 AS DateTime)) INSERT [dbo].[orders] ([orderId], [tradeId], [amount], [buySell], [rate], [orderDateTime]) VALUES (34, 10, CAST(1.0 AS Decimal(18, 1)), N'S', CAST(1.619000 AS Decimal(18, 6)), CAST(0x00009D0A0083D600 AS DateTime)) SET IDENTITY_INSERT [dbo].[orders] OFF /****** Object: ForeignKey [FK_orders_trades] Script Date: 04/02/2010 15:05:31 ******/ ALTER TABLE [dbo].[orders] WITH CHECK ADD CONSTRAINT [FK_orders_trades] FOREIGN KEY([tradeId]) REFERENCES [dbo].[trades] ([tradeId]) GO ALTER TABLE [dbo].[orders] CHECK CONSTRAINT [FK_orders_trades] GO Thanks in advance for any help!

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  • Template inheritence c++

    - by Chris Condy
    I have made a template singleton class, I have also made a data structure that is templated. My question is; how do I make my templated data structure inherit from a singleton so you can only have one float type of this structure? I have tested both seperate and have found no problems. Code provided under... (That is the problem) template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > The problem is the code above doesn't work I get alot of errors. I cant get it to no matter what I do template a templated singleton class... I was asking for maybe advice or maybe if the code above is incorrect guidence? #ifndef SINGLETON_H #define SINGLETON_H template <class Type> class Singleton { public: virtual ~Singleton(); Singleton(); static Type* m_instance; }; template <class Type> Type* Singleton<Type>::m_instance = 0; #include "Singleton.cpp" #endif #ifndef SINGLETON_CPP #define SINGLETON_CPP #include "Singleton.h" template <class Type> Singleton<Type>::Singleton() { } template <class Type> Singleton<Type>::~Singleton() { } template <class Type> Type* Singleton<Type>::getInstance() { if(m_instance==nullptr) { m_instance = new Type; } return m_instance; } #endif #ifndef ABSTRACTRMANAGERS_H #define ABSTRACTRMANAGERS_H #include <vector> #include <map> #include <stack> #include "Singleton.h" template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > { public: virtual ~AbstractRManagers(); int insert(Type* type, std::string name); Type* remove(int i); Type* remove(std::string name); Type* get(int i); Type* getS(std::string name); int get(std::string name); int get(Type* i); bool check(std::string name); int resourceSize(); protected: private: std::vector<Type*> m_resources; std::map<std::string,int> m_map; std::stack<int> m_freePos; }; #include "AbstractRManagers.cpp" #endif #ifndef ABSTRACTRMANAGERS_CPP #define ABSTRACTRMANAGERS_CPP #include "AbstractRManagers.h" template <class Type> int AbstractRManagers<Type>::insert(Type* type, std::string name) { int i=0; if(!check(name)) { if(m_freePos.empty()) { m_resources.push_back(type); i = m_resources.size()-1; m_map[name] = i; } else { i = m_freePos.top(); m_freePos.pop(); m_resources[i] = type; m_map[name] = i; } } else i = -1; return i; } template <class Type> int AbstractRManagers<Type>::resourceSize() { return m_resources.size(); } template <class Type> bool AbstractRManagers<Type>::check(std::string name) { std::map<std::string,int>::iterator it; it = m_map.find(name); if(it==m_map.end()) return false; return true; } template <class Type> Type* AbstractRManagers<Type>::remove(std::string name) { Type* temp = m_resources[m_map[name]]; if(temp!=NULL) { std::map<std::string,int>::iterator it; it = m_map[name]; m_resources[m_map[name]] = NULL; m_freePos.push(m_map[name]); delete (*it).second; delete (*it).first; return temp; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::remove(int i) { if((i < m_resources.size())&&(i > 0)) { Type* temp = m_resources[i]; m_resources[i] = NULL; m_freePos.push(i); std::map<std::string,int>::iterator it; for(it=m_map.begin();it!=m_map.end();it++) { if((*it).second == i) { delete (*it).second; delete (*it).first; return temp; } } return temp; } return NULL; } template <class Type> int AbstractRManagers<Type>::get(Type* i) { for(int i2=0;i2<m_resources.size();i2++) { if(i == m_resources[i2]) { return i2; } } return -1; } template <class Type> Type* AbstractRManagers<Type>::get(int i) { if((i < m_resources.size())&&(i >= 0)) { return m_resources[i]; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::getS(std::string name) { return m_resources[m_map[name]]; } template <class Type> int AbstractRManagers<Type>::get(std::string name) { return m_map[name]; } template <class Type> AbstractRManagers<Type>::~AbstractRManagers() { } #endif #include "AbstractRManagers.h" struct b { float x; }; int main() { b* a = new b(); AbstractRManagers<b>::getInstance()->insert(a,"a"); return 0; } This program produces next errors when compiled : 1> main.cpp 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1> c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(124) : while compiling class template member function 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const' 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(71) : see reference to class template instantiation 'std::less<_Ty>' being compiled 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(451) : see reference to class template instantiation 'std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,_Mfl>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int, 1> _Pr=std::less<std::string>, 1> _Alloc=std::allocator<std::pair<const std::string,int>>, 1> _Mfl=false 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(520) : see reference to class template instantiation 'std::_Tree_nod<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(659) : see reference to class template instantiation 'std::_Tree_val<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(81) : see reference to class template instantiation 'std::_Tree<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(28) : see reference to class template instantiation 'std::map<_Kty,_Ty>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(30) : see reference to class template instantiation 'AbstractRManagers<Type>' being compiled 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2676: binary '<' : 'const std::string' does not define this operator or a conversion to a type acceptable to the predefined operator ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

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  • Does it ever make sense to make a fundamental (non-pointer) parameter const?

    - by Scott Smith
    I recently had an exchange with another C++ developer about the following use of const: void Foo(const int bar); He felt that using const in this way was good practice. I argued that it does nothing for the caller of the function (since a copy of the argument was going to be passed, there is no additional guarantee of safety with regard to overwrite). In addition, doing this prevents the implementer of Foo from modifying their private copy of the argument. So, it both mandates and advertises an implementation detail. Not the end of the world, but certainly not something to be recommended as good practice. I'm curious as to what others think on this issue. Edit: OK, I didn't realize that const-ness of the arguments didn't factor into the signature of the function. So, it is possible to mark the arguments as const in the implementation (.cpp), and not in the header (.h) - and the compiler is fine with that. That being the case, I guess the policy should be the same for making local variables const. One could make the argument that having different looking signatures in the header and source file would confuse others (as it would have confused me). While I try to follow the Principle of Least Astonishment with whatever I write, I guess it's reasonable to expect developers to recognize this as legal and useful.

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  • const TypedeffedIntPointer not equal to const int *

    - by dirk
    I have the following C++ code: typedef int* IntPtr; const int* cip = new int; const IntPtr ctip4 = cip; I compile this with Visual Studio 2008 and get the following error: error C2440: 'initializing' : cannot convert from 'const int *' to 'const IntPtr' Clearly my understanding of typedefs is not what is should be. The reason I'm asking, I'm storing a pointer type in a STL map. I have a function that returns a const pointer which I would like to use to search in the map (using map::find(const key_type&). Since const MyType* and const map<MyType*, somedata>::key_type is incompatible, I'm having problems. Regards Dirk

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  • const member functions can call const member functions only?

    - by Abhi
    Hi all. Do const member functions call only const member functions? class Transmitter{ const static string msg; mutable int size; public: void xmit() const{ size = compute(); cout<<msg; } private: int compute() const{return 5;} }; string const Transmitter::msg = "beep"; int main(){ Transmitter t; t.xmit(); return EXIT_SUCCESS; } If i dont make compute() a const, then the compiler complains. Is it because since a const member function is not allowed to modify members, it wont allow any calls to non-consts since it would mean that the const member function would be 'indirectly' modifying the data members?

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  • Higher order function « filter » in C++

    - by Red Hyena
    Hi all. I wanted to write a higher order function filter with C++. The code I have come up with so far is as follows: #include <iostream> #include <string> #include <functional> #include <algorithm> #include <vector> #include <list> #include <iterator> using namespace std; bool isOdd(int const i) { return i % 2 != 0; } template < template <class, class> class Container, class Predicate, class Allocator, class A > Container<A, Allocator> filter(Container<A, Allocator> const & container, Predicate const & pred) { Container<A, Allocator> filtered(container); container.erase(remove_if(filtered.begin(), filtered.end(), pred), filtered.end()); return filtered; } int main() { int const a[] = {23, 12, 78, 21, 97, 64}; vector<int const> const v(a, a + 6); vector<int const> const filtered = filter(v, isOdd); copy(filtered.begin(), filtered.end(), ostream_iterator<int const>(cout, " ")); } However on compiling this code, I get the following error messages that I am unable to understand and hence get rid of: /usr/include/c++/4.3/ext/new_allocator.h: In instantiation of ‘__gnu_cxx::new_allocator<const int>’: /usr/include/c++/4.3/bits/allocator.h:84: instantiated from ‘std::allocator<const int>’ /usr/include/c++/4.3/bits/stl_vector.h:75: instantiated from ‘std::_Vector_base<const int, std::allocator<const int> >’ /usr/include/c++/4.3/bits/stl_vector.h:176: instantiated from ‘std::vector<const int, std::allocator<const int> >’ Filter.cpp:29: instantiated from here /usr/include/c++/4.3/ext/new_allocator.h:82: error: ‘const _Tp* __gnu_cxx::new_allocator<_Tp>::address(const _Tp&) const [with _Tp = const int]’ cannot be overloaded /usr/include/c++/4.3/ext/new_allocator.h:79: error: with ‘_Tp* __gnu_cxx::new_allocator<_Tp>::address(_Tp&) const [with _Tp = const int]’ Filter.cpp: In function ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’: Filter.cpp:30: instantiated from here Filter.cpp:23: error: passing ‘const std::vector<const int, std::allocator<const int> >’ as ‘this’ argument of ‘__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> > std::vector<_Tp, _Alloc>::erase(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, __gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >) [with _Tp = const int, _Alloc = std::allocator<const int>]’ discards qualifiers /usr/include/c++/4.3/bits/stl_algo.h: In function ‘_FIter std::remove_if(_FIter, _FIter, _Predicate) [with _FIter = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _Predicate = bool (*)(int)]’: Filter.cpp:23: instantiated from ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’ Filter.cpp:30: instantiated from here /usr/include/c++/4.3/bits/stl_algo.h:821: error: assignment of read-only location ‘__result.__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator* [with _Iterator = const int*, _Container = std::vector<const int, std::allocator<const int> >]()’ /usr/include/c++/4.3/ext/new_allocator.h: In member function ‘void __gnu_cxx::new_allocator<_Tp>::deallocate(_Tp*, size_t) [with _Tp = const int]’: /usr/include/c++/4.3/bits/stl_vector.h:150: instantiated from ‘void std::_Vector_base<_Tp, _Alloc>::_M_deallocate(_Tp*, size_t) [with _Tp = const int, _Alloc = std::allocator<const int>]’ /usr/include/c++/4.3/bits/stl_vector.h:136: instantiated from ‘std::_Vector_base<_Tp, _Alloc>::~_Vector_base() [with _Tp = const int, _Alloc = std::allocator<const int>]’ /usr/include/c++/4.3/bits/stl_vector.h:286: instantiated from ‘std::vector<_Tp, _Alloc>::vector(_InputIterator, _InputIterator, const _Alloc&) [with _InputIterator = const int*, _Tp = const int, _Alloc = std::allocator<const int>]’ Filter.cpp:29: instantiated from here /usr/include/c++/4.3/ext/new_allocator.h:98: error: invalid conversion from ‘const void*’ to ‘void*’ /usr/include/c++/4.3/ext/new_allocator.h:98: error: initializing argument 1 of ‘void operator delete(void*)’ /usr/include/c++/4.3/bits/stl_algobase.h: In function ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false, _II = const int*, _OI = const int*]’: /usr/include/c++/4.3/bits/stl_algobase.h:435: instantiated from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false, _II = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _OI = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >]’ /usr/include/c++/4.3/bits/stl_algobase.h:466: instantiated from ‘_OI std::copy(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _OI = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >]’ /usr/include/c++/4.3/bits/vector.tcc:136: instantiated from ‘__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> > std::vector<_Tp, _Alloc>::erase(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, __gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >) [with _Tp = const int, _Alloc = std::allocator<const int>]’ Filter.cpp:23: instantiated from ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’ Filter.cpp:30: instantiated from here /usr/include/c++/4.3/bits/stl_algobase.h:396: error: no matching function for call to ‘std::__copy_move<false, true, std::random_access_iterator_tag>::__copy_m(const int*&, const int*&, const int*&)’ Please tell me what I am doing wrong here and what is the correct way to achieve the kind of higher order polymorphism I want. Thanks.

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  • A mysterious compilation error: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>'

    - by Stephane Rolland
    I wanted to protect the access to a log file that I use for multithreaded logging with boostlog library. I tried this stream class class ThreadSafeStream { public: template <typename TInput> const ThreadSafeStream& operator<< (const TInput &tInput) const { // some thread safe file access return *this; } }; using it this way (text_sink is a boostlog object): //... m_spSink.reset(new text_sink); text_sink::locked_backend_ptr pBackend = m_spSink->locked_backend(); const boost::shared_ptr< ThreadSafeStream >& spFileStream = boost::make_shared<ThreadSafeStream>(); pBackend->add_stream(spFileStream); // this causes the compilation error and I get this mysterious error: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>' the whole compile error: Log.cpp(79): error C2664: 'boost::log2_mt_nt5::sinks::basic_text_ostream_backend<CharT>::add_stream' : cannot convert parameter 1 from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T> &' 1> with 1> [ 1> CharT=char 1> ] 1> and 1> [ 1> T=ThreadSafeStream 1> ] 1> and 1> [ 1> T=std::basic_ostream<char,std::char_traits<char>> 1> ] 1> Reason: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>' 1> with 1> [ 1> T=ThreadSafeStream 1> ] 1> and 1> [ 1> T=std::basic_ostream<char,std::char_traits<char>> 1> ] 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called I suspect that I am not well defining the operator<<()... but I don't find what is wrong.

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  • Allow member to be const while still supporting operator= on the class

    - by LeopardSkinPillBoxHat
    I have several members in my class which are const and can therefore only be initialised via the initialiser list like so: class MyItemT { public: MyItemT(const MyPacketT& aMyPacket, const MyInfoT& aMyInfo) : mMyPacket(aMyPacket), mMyInfo(aMyInfo) { } private: const MyPacketT mMyPacket; const MyInfoT mMyInfo; }; My class can be used in some of our internally defined container classes (e.g. vectors), and these containers require that operator= is defined in the class. Of course, my operator= needs to do something like this: MyItemT& MyItemT::operator=(const MyItemT& other) { mMyPacket = other.mPacket; mMyInfo = other.mMyInfo; return *this; } which of course doesn't work because mMyPacket and mMyInfo are const members. Other than making these members non-const (which I don't want to do), any ideas about how I could fix this?

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  • const return value and template instantiation

    - by Rimo
    From Herb Sutter's GotW #6 Return-by-value should normally be const for non-builtin return types. .... Note: Lakos (pg. 618) argues against returning const value, and notes that it is redundant for builtins anyway (for example, returning "const int"), which he notes may interfere with template instantiation. .... While Sutter seems to disagree on whether to return a const value or non-const value when returning an object of a non-built type by value with Lakos, he generally agrees that returning a const value of a built-in type (e.g const int) is not a good idea. While I understand why that is useless because the return value cannot be modified as it is an rvalue, I cannot find an example of how that might interfere with template instantiation. Please give me an example of how having a const qualifier for a return type might interfere with template instantiation.

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  • g++ linker can't find const member function

    - by Max
    I have a Point class (with integer members x and y) that has a member function withinBounds that is declared like so: bool withinBounds(const Point&, const Point&) const; and defined like this: bool Point::withinBounds(const Point& TL, const Point& BR) const { if(x < TL.getX()) return false; if(x > BR.getX()) return false; if(y < TL.getY()) return false; if(y > BR.getY()) return false; // Success return true; } and then in another file, I call withinBounds like this: Point pos = currentPlayer->getPosition(); if(pos.withinBounds(topleft, bottomright)) { // code block } This compiles fine, but it fails to link. g++ gives me this error: /home/max/Desktop/Development/YARL/yarl/src/GameData.cpp:61: undefined reference to 'yarl::utility::Point::withinBounds(yarl::utility::Point const&, yarl::utility::Point const&)' When I make the function not const, it links fine. Anyone know the reason why? The linker error looks like it's looking for a non-const version of the function, but I don't know why it would.

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  • Is it appropriate to set a value to a "const char *" in the header file

    - by sud
    I have seen people using 2 methods to declare and define char * Medhod-1: The header file has the below const char* COUNTRY_NAME_USA = "USA"; Medhod-2: The header file has the below declaration const char* COUNTRY_NAME_USA; The cpp file has the below defintion : const char* COUNTRY_NAME_USA = "USA"; Is method-2 wrong in some way ? What is the difference between the two ? I understand the difference between "const char * const var" , and "const char * var". If in the above methods if a "const char * const var" is declared and defined in the header as in method 1 will it make sense ?

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  • Simplifying const Overloading?

    - by templatetypedef
    Hello all- I've been teaching a C++ programming class for many years now and one of the trickiest things to explain to students is const overloading. I commonly use the example of a vector-like class and its operator[] function: template <typename T> class Vector { public: T& operator[] (size_t index); const T& operator[] (size_t index) const; }; I have little to no trouble explaining why it is that two versions of the operator[] function are needed, but in trying to explain how to unify the two implementations together I often find myself wasting a lot of time with language arcana. The problem is that the only good, reliable way that I know how to implement one of these functions in terms of the other is with the const_cast/static_cast trick: template <typename T> const T& Vector<T>::operator[] (size_t index) const { /* ... your implementation here ... */ } template <typename T> T& Vector<T>::operator[] (size_t index) { return const_cast<T&>(static_cast<const Vector&>(*this)[index]); } The problem with this setup is that it's extremely tricky to explain and not at all intuitively obvious. When you explain it as "cast to const, then call the const version, then strip off constness" it's a little easier to understand, but the actual syntax is frightening,. Explaining what const_cast is, why it's appropriate here, and why it's almost universally inappropriate elsewhere usually takes me five to ten minutes of lecture time, and making sense of this whole expression often requires more effort than the difference between const T* and T* const. I feel that students need to know about const-overloading and how to do it without needlessly duplicating the code in the two functions, but this trick seems a bit excessive in an introductory C++ programming course. My question is this - is there a simpler way to implement const-overloaded functions in terms of one another? Or is there a simpler way of explaining this existing trick to students? Thanks so much!

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  • C++: get const or non-const reference type from trait

    - by maciekp
    I am writing a functor F which takes function of type void (*func)(T) and func's argument arg. Then functor F calls func with arg. I would like F not to copy arg, just to pass it as reference. But then I cannot simply write "void F(void (*func)(T), T&)" because T could be a reference. So I am trying to write a trait, which allows to get proper reference type of T: T -> T& T& -> T& const T -> const T& const T& -> const T& I come up with something like this: template<typename T> struct type_op { typedef T& valid_ref_type; }; template<typename T> struct type_op<T&> { typedef typename type_op<T>::valid_ref_type valid_ref_type; }; template<typename T> struct type_op<const T> { typedef const T& valid_ref_type; }; template<typename T> struct type_op<const T&> { typedef const T& valid_ref_type; }; Which doesn't work for example for void a(int x) { std::cout << x << std::endl; } F(&a, 7); Giving error: invalid initialization of non-const reference of type ‘int&’ from a temporary of type ‘int’ in passing argument 2 of ‘void f(void (*)(T), typename type_op::valid_ref_type) [with T = int]’ How to get this trait to work?

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  • Passing const CName as this argument discards qualifiers

    - by Geno Diaz
    I'm having trouble with passing a constant class through a function. // test the constructors auto CName nameOne("Robert", "Bresson"); const CName nameTwo = nameOne; auto CName nameThree; // display the contents of each newly-constructed object... // should see "Robert Bresson" cout << "nameOne = "; nameOne.WriteFullName(); cout << endl; // should see "Robert Bresson" again cout << "nameTwo = "; nameTwo.WriteFullName(); cout << endl; As soon as the compiler hits nameTwo.WriteFullName() I get the error of abandoning qualifiers. I know that the class is a constant however I can't figure out how to work around it. The function is in a header file written as so: void const WriteFullName(ostream& outstream = cout) { outstream << m_first << ' ' << m_last; } I receive this error when const is put in back of the function header main.cpp:(.text+0x51): undefined reference to CName::CName()' main.cpp:(.text+0x7c): undefined reference toCName::WriteFullName(std::basic_ostream &) const' main.cpp:(.text+0xbb): undefined reference to CName::WriteFullName(std::basic_ostream<char, std::char_traits<char> >&) const' main.cpp:(.text+0xf7): undefined reference toCName::WriteFullName(std::basic_ostream &) const' main.cpp:(.text+0x133): undefined reference to operator>>(std::basic_istream<char, std::char_traits<char> >&, CName&)' main.cpp:(.text+0x157): undefined reference tooperator<<(std::basic_ostream &, CName const&)' main.cpp:(.text+0x1f4): undefined reference to operator<<(std::basic_ostream<char, std::char_traits<char> >&, CName const&)' main.cpp:(.text+0x22b): undefined reference tooperator<<(std::basic_ostream &, CName const&)' main.cpp:(.text+0x25f): undefined reference to operator<<(std::basic_ostream<char, std::char_traits<char> >&, CName const&)' main.cpp:(.text+0x320): undefined reference tooperator<<(std::basic_ostream &, CName const&)' main.cpp:(.text+0x347): undefined reference to `operator(std::basic_istream &, CName&)'

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  • How to provide stl like container with public const iterator and private non-const iterator?

    - by WilliamKF
    Hello, I am deriving a class privately from std::list and wish to provide public begin() and end() for const_iterator and private begin() and end() for just plain iterator. However, the compiler is seeing the private version and complaining that it is private instead of using the public const version. I understand that C++ will not overload on return type (in this case const_iterator and iterator) and thus it is choosing the non-const version since my object is not const. Short of casting my object to const before calling begin() or not overloading the name begin is there a way to accomplish this? I would think this is a known pattern that folks have solved before and would like to follow suit as to how this is typically solved. class myObject; class myContainer : private std::list<myObject> { public: typedef std::list<myObject>::const_iterator myContainer::const_iterator; private: typedef std::list<myObject>::iterator myContainer::iterator; public: myContainer::const_iterator begin() const { return std::list<myObject>::begin(); } myContainer::const_iterator end() const { return std::list<myObject>::end(); } private: myContainer::iterator begin() { return std::list<myObject>::begin(); } myContainer::iterator end() { return std::list<myObject>::end(); } }; void myFunction(myContainer &container) { myContainer::const_iterator aItr = container.begin(); myContainer::const_iterator aEndItr = container.end(); for (; aItr != aEndItr; ++aItr) { const myObject &item = *aItr; // Do something const on container's contents. } } The error from the compiler is something like this: ../../src/example.h:447: error: `std::_List_iterator<myObject> myContainer::begin()' is private caller.cpp:2393: error: within this context ../../src/example.h:450: error: `std::_List_iterator<myObject> myContainer::end()' is private caller.cpp:2394: error: within this context Thanks. -William

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