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  • introducing pointers to a large software project

    - by stefan
    I have a fairly large software project written in c++. In there, there is a class foo which represents a structure (by which i don't mean the programmers struct) in which foo-objects can be part of a foo-object. Here's class foo in simplest form: class Foo { private: std::vector<unsigned int> indices; public: void addFooIndex(unsigned int); unsigned int getFooIndex(unsigned int); }; Every foo-object is currently stored in an object of class bar. class Bar { private: std::vector<Foo> foos; public: void addFoo(Foo); std::vector<Foo> getFoos(); } So if a foo-object should represent a structure with a "inner" foo-object, I currently do Foo foo; Foo innerFoo; foo.addFooIndex(bar.getFoos().size() - 1); bar.addFoo(innerFoo); And to get it, I obviously use: Foo foo; for ( unsigned int i = 0; i < foo.getFooIndices().size(); ++i ) { Foo inner_foo; assert( foo.getFooIndices().at(i) < bar.getFoos().size() ); inner_foo = bar.getFoos().at(foo.getFooIndices().at(i)); } So this is not a problem. It just works. But it's not the most elegant solution. I now want to make the inner foos to be "more connected" with the foo-object. It would be obviously to change class foo to: class Foo { private: std::vector<Foo*> foo_pointers; public: void addFooPointer(Foo*); std::vector<Foo*> getFooPointers(); }; So now, for my question: How to gently change this basic class without messing up the whole code? Is there a "clean way"?

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  • Weird behavior when using pointers [migrated]

    - by Kinan Al Sarmini
    When I run this code on MS VS C++ 2010: #include <iostream> int main() { const int a = 10; const int *b = &a; int *c = (int *)b; *c = 10000; std::cout << c << " " << &a << std::endl; std::cout << *c << " " << a << " " << *(&a) << std::endl; return 0; } The output is: 0037F784 0037F784 10000 10 10 The motivation for writing that code was this sentence from "The C++ Programming Language" by Stroustrup: "It is possible to explicitly remove the restrictions on a pointer to const by explicit type conversion". I know that trying to modify a constant is conceptually wrong, but I find this result quite weird. Can anyone explain the reason behind it?

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  • function pointers callbacks C

    - by robUK
    Hello, I have started to review callbacks. I found this link: http://stackoverflow.com/questions/142789/what-is-a-callback-in-c-and-how-are-they-implemented which has a good example of callback which is very similar to what we use at work. However, I have tried to get it to work, but I have many errors. #include <stdio.h> /* Is the actual function pointer? */ typedef void (*event_cb_t)(const struct event *evt, void *user_data); struct event_cb { event_cb_t cb; void *data; }; int event_cb_register(event_ct_t cb, void *user_data); static void my_event_cb(const struct event *evt, void *data) { /* do some stuff */ } int main(void) { event_cb_register(my_event_cb, &my_custom_data); struct event_cb *callback; callback->cb(event, callback->data); return 0; } I know that callback use function pointers to store an address of a function. But there is a few things that I find I don't understand. That is what is meet by "registering the callback" and "event dispatcher"? Many thanks for any advice,

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  • Invalid conversion from int to int** C++

    - by user69514
    Not sure why I'm getting this error. I have the following: int* arr = new int[25]; int* foo(){ int* i; cout << "Enter an integer:"; cin >> *i; return i; } void test(int** myInt){ *myInt = foo(); } This call here is where I get the error: test(arr[0]); //here i get invalid conversion from int to int**

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  • Function pointer demo

    - by AKN
    Hi, Check the below code void functionptrdemo() { typedef int *(funcPtr) (int,int); funcPtr ptr; ptr = add; //IS THIS CORRECT? (*ptr)(2,3); } In the place where I try to assign a function to function ptr with same function signature, it shows a compilation error as error C2659: '=' : function as left operand

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  • eventmachine on debian fails install via rubygems

    - by Max
    this has been killing me for the last 5 hours. I don't seem to be able to get eventmachine running on my debian box. here this output: $ gem install thin Building native extensions. This could take a while... ERROR: Error installing thin: ERROR: Failed to build gem native extension. /home/eventhub/.rvm/rubies/ruby-1.9.3-p125/bin/ruby extconf.rb checking for rb_trap_immediate in ruby.h,rubysig.h... no checking for rb_thread_blocking_region()... yes checking for inotify_init() in sys/inotify.h... yes checking for writev() in sys/uio.h... yes checking for rb_wait_for_single_fd()... yes checking for rb_enable_interrupt()... yes checking for rb_time_new()... yes checking for sys/event.h... no checking for epoll_create() in sys/epoll.h... yes creating Makefile make compiling kb.cpp cc1plus: warning: command line option "-Wdeclaration-after-statement" is valid for C/ObjC but not for C++ cc1plus: warning: command line option "-Wimplicit-function-declaration" is valid for C/ObjC but not for C++ In file included from project.h:149, from kb.cpp:20: binder.h:35: warning: type qualifiers ignored on function return type In file included from project.h:150, from kb.cpp:20: em.h:84: warning: type qualifiers ignored on function return type em.h:85: warning: type qualifiers ignored on function return type em.h:86: warning: type qualifiers ignored on function return type em.h:88: warning: type qualifiers ignored on function return type em.h:89: warning: type qualifiers ignored on function return type em.h:90: warning: type qualifiers ignored on function return type em.h:91: warning: type qualifiers ignored on function return type em.h:93: warning: type qualifiers ignored on function return type em.h:99: warning: type qualifiers ignored on function return type em.h:116: warning: type qualifiers ignored on function return type em.h:125: warning: type qualifiers ignored on function return type In file included from project.h:154, from kb.cpp:20: eventmachine.h:46: warning: type qualifiers ignored on function return type eventmachine.h:47: warning: type qualifiers ignored on function return type eventmachine.h:48: warning: type qualifiers ignored on function return type eventmachine.h:50: warning: type qualifiers ignored on function return type eventmachine.h:65: warning: type qualifiers ignored on function return type eventmachine.h:66: warning: type qualifiers ignored on function return type eventmachine.h:67: warning: type qualifiers ignored on function return type eventmachine.h:68: warning: type qualifiers ignored on function return type In file included from project.h:154, from kb.cpp:20: eventmachine.h:103: warning: type qualifiers ignored on function return type eventmachine.h:105: warning: type qualifiers ignored on function return type eventmachine.h:108: warning: type qualifiers ignored on function return type compiling rubymain.cpp cc1plus: warning: command line option "-Wdeclaration-after-statement" is valid for C/ObjC but not for C++ cc1plus: warning: command line option "-Wimplicit-function-declaration" is valid for C/ObjC but not for C++ In file included from project.h:149, from rubymain.cpp:20: binder.h:35: warning: type qualifiers ignored on function return type In file included from project.h:150, from rubymain.cpp:20: em.h:84: warning: type qualifiers ignored on function return type em.h:85: warning: type qualifiers ignored on function return type em.h:86: warning: type qualifiers ignored on function return type em.h:88: warning: type qualifiers ignored on function return type em.h:89: warning: type qualifiers ignored on function return type em.h:90: warning: type qualifiers ignored on function return type em.h:91: warning: type qualifiers ignored on function return type em.h:93: warning: type qualifiers ignored on function return type em.h:99: warning: type qualifiers ignored on function return type em.h:116: warning: type qualifiers ignored on function return type em.h:125: warning: type qualifiers ignored on function return type In file included from project.h:154, from rubymain.cpp:20: eventmachine.h:46: warning: type qualifiers ignored on function return type eventmachine.h:47: warning: type qualifiers ignored on function return type eventmachine.h:48: warning: type qualifiers ignored on function return type eventmachine.h:50: warning: type qualifiers ignored on function return type eventmachine.h:65: warning: type qualifiers ignored on function return type eventmachine.h:66: warning: type qualifiers ignored on function return type eventmachine.h:67: warning: type qualifiers ignored on function return type eventmachine.h:68: warning: type qualifiers ignored on function return type In file included from project.h:154, from rubymain.cpp:20: eventmachine.h:103: warning: type qualifiers ignored on function return type eventmachine.h:105: warning: type qualifiers ignored on function return type eventmachine.h:108: warning: type qualifiers ignored on function return type compiling ssl.cpp cc1plus: warning: command line option "-Wdeclaration-after-statement" is valid for C/ObjC but not for C++ cc1plus: warning: command line option "-Wimplicit-function-declaration" is valid for C/ObjC but not for C++ In file included from project.h:149, from ssl.cpp:23: binder.h:35: warning: type qualifiers ignored on function return type In file included from project.h:150, from ssl.cpp:23: em.h:84: warning: type qualifiers ignored on function return type em.h:85: warning: type qualifiers ignored on function return type em.h:86: warning: type qualifiers ignored on function return type em.h:88: warning: type qualifiers ignored on function return type em.h:89: warning: type qualifiers ignored on function return type em.h:90: warning: type qualifiers ignored on function return type em.h:91: warning: type qualifiers ignored on function return type em.h:93: warning: type qualifiers ignored on function return type em.h:99: warning: type qualifiers ignored on function return type em.h:116: warning: type qualifiers ignored on function return type em.h:125: warning: type qualifiers ignored on function return type In file included from project.h:154, from ssl.cpp:23: eventmachine.h:46: warning: type qualifiers ignored on function return type eventmachine.h:47: warning: type qualifiers ignored on function return type eventmachine.h:48: warning: type qualifiers ignored on function return type eventmachine.h:50: warning: type qualifiers ignored on function return type eventmachine.h:65: warning: type qualifiers ignored on function return type eventmachine.h:66: warning: type qualifiers ignored on function return type eventmachine.h:67: warning: type qualifiers ignored on function return type eventmachine.h:68: warning: type qualifiers ignored on function return type In file included from project.h:154, from ssl.cpp:23: eventmachine.h:103: warning: type qualifiers ignored on function return type eventmachine.h:105: warning: type qualifiers ignored on function return type eventmachine.h:108: warning: type qualifiers ignored on function return type compiling cmain.cpp cc1plus: warning: command line option "-Wdeclaration-after-statement" is valid for C/ObjC but not for C++ cc1plus: warning: command line option "-Wimplicit-function-declaration" is valid for C/ObjC but not for C++ In file included from project.h:149, from cmain.cpp:20: binder.h:35: warning: type qualifiers ignored on function return type In file included from project.h:150, from cmain.cpp:20: em.h:84: warning: type qualifiers ignored on function return type em.h:85: warning: type qualifiers ignored on function return type em.h:86: warning: type qualifiers ignored on function return type em.h:88: warning: type qualifiers ignored on function return type em.h:89: warning: type qualifiers ignored on function return type em.h:90: warning: type qualifiers ignored on function return type em.h:91: warning: type qualifiers ignored on function return type em.h:93: warning: type qualifiers ignored on function return type em.h:99: warning: type qualifiers ignored on function return type em.h:116: warning: type qualifiers ignored on function return type em.h:125: warning: type qualifiers ignored on function return type In file included from project.h:154, from cmain.cpp:20: eventmachine.h:46: warning: type qualifiers ignored on function return type eventmachine.h:47: warning: type qualifiers ignored on function return type eventmachine.h:48: warning: type qualifiers ignored on function return type eventmachine.h:50: warning: type qualifiers ignored on function return type eventmachine.h:65: warning: type qualifiers ignored on function return type eventmachine.h:66: warning: type qualifiers ignored on function return type eventmachine.h:67: warning: type qualifiers ignored on function return type eventmachine.h:68: warning: type qualifiers ignored on function return type In file included from project.h:154, from cmain.cpp:20: eventmachine.h:103: warning: type qualifiers ignored on function return type eventmachine.h:105: warning: type qualifiers ignored on function return type eventmachine.h:108: warning: type qualifiers ignored on function return type cmain.cpp:96: warning: type qualifiers ignored on function return type cmain.cpp:107: warning: type qualifiers ignored on function return type cmain.cpp:117: warning: type qualifiers ignored on function return type cmain.cpp:127: warning: type qualifiers ignored on function return type cmain.cpp:269: warning: type qualifiers ignored on function return type cmain.cpp:279: warning: type qualifiers ignored on function return type cmain.cpp:289: warning: type qualifiers ignored on function return type cmain.cpp:299: warning: type qualifiers ignored on function return type cmain.cpp:309: warning: type qualifiers ignored on function return type cmain.cpp:329: warning: type qualifiers ignored on function return type cmain.cpp:678: warning: type qualifiers ignored on function return type compiling em.cpp cc1plus: warning: command line option "-Wdeclaration-after-statement" is valid for C/ObjC but not for C++ cc1plus: warning: command line option "-Wimplicit-function-declaration" is valid for C/ObjC but not for C++ In file included from project.h:149, from em.cpp:23: binder.h:35: warning: type qualifiers ignored on function return type In file included from project.h:150, from em.cpp:23: em.h:84: warning: type qualifiers ignored on function return type em.h:85: warning: type qualifiers ignored on function return type em.h:86: warning: type qualifiers ignored on function return type em.h:88: warning: type qualifiers ignored on function return type em.h:89: warning: type qualifiers ignored on function return type em.h:90: warning: type qualifiers ignored on function return type em.h:91: warning: type qualifiers ignored on function return type em.h:93: warning: type qualifiers ignored on function return type em.h:99: warning: type qualifiers ignored on function return type em.h:116: warning: type qualifiers ignored on function return type em.h:125: warning: type qualifiers ignored on function return type In file included from project.h:154, from em.cpp:23: eventmachine.h:46: warning: type qualifiers ignored on function return type eventmachine.h:47: warning: type qualifiers ignored on function return type eventmachine.h:48: warning: type qualifiers ignored on function return type eventmachine.h:50: warning: type qualifiers ignored on function return type eventmachine.h:65: warning: type qualifiers ignored on function return type eventmachine.h:66: warning: type qualifiers ignored on function return type eventmachine.h:67: warning: type qualifiers ignored on function return type eventmachine.h:68: warning: type qualifiers ignored on function return type In file included from project.h:154, from em.cpp:23: eventmachine.h:103: warning: type qualifiers ignored on function return type eventmachine.h:105: warning: type qualifiers ignored on function return type eventmachine.h:108: warning: type qualifiers ignored on function return type em.cpp: In member function 'bool EventMachine_t::_RunEpollOnce()': em.cpp:578: warning: 'int rb_thread_select(int, fd_set*, fd_set*, fd_set*, timeval*)' is deprecated (declared at /home/eventhub/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/ruby/intern.h:379) em.cpp:578: warning: 'int rb_thread_select(int, fd_set*, fd_set*, fd_set*, timeval*)' is deprecated (declared at /home/eventhub/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/ruby/intern.h:379) em.cpp: In member function 'bool EventMachine_t::_RunSelectOnce()': em.cpp:974: warning: 'int rb_thread_select(int, fd_set*, fd_set*, fd_set*, timeval*)' is deprecated (declared at /home/eventhub/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/ruby/intern.h:379) em.cpp:974: warning: 'int rb_thread_select(int, fd_set*, fd_set*, fd_set*, timeval*)' is deprecated (declared at /home/eventhub/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/ruby/intern.h:379) em.cpp: At global scope: em.cpp:1057: warning: type qualifiers ignored on function return type em.cpp:1079: warning: type qualifiers ignored on function return type em.cpp:1265: warning: type qualifiers ignored on function return type em.cpp:1338: warning: type qualifiers ignored on function return type em.cpp:1510: warning: type qualifiers ignored on function return type em.cpp:1593: warning: type qualifiers ignored on function return type em.cpp:1856: warning: type qualifiers ignored on function return type em.cpp:1982: warning: type qualifiers ignored on function return type em.cpp:2046: warning: type qualifiers ignored on function return type em.cpp:2070: warning: type qualifiers ignored on function return type em.cpp:2142: warning: type qualifiers ignored on function return type em.cpp:2361: fatal error: error writing to /tmp/ccdlOK0T.s: No space left on device compilation terminated. make: *** [em.o] Error 1 Gem files will remain installed in /home/eventhub/.rvm/gems/ruby-1.9.3-p125/gems/eventmachine-1.0.1 for inspection. Results logged to /home/eventhub/.rvm/gems/ruby-1.9.3-p125/gems/eventmachine-1.0.1/ext/gem_make.out Any thoughts? I read a lot of different ways to solve this issue, but none of them worked. Thanks

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  • invasive vs non-invasive ref-counted pointers in C++

    - by anon
    For the past few years, I've generally accepted that if I am going to use ref-counted smart pointers invasive smart pointers is the way to go -- However, I'm starting to like non-invasive smart pointers due to the following: I only use smart pointers (so no Foo* lying around, only Ptr) I'm starting to build custom allocators for each class. (So Foo would overload operator new). Now, if Foo has a list of all Ptr (as it easily can with non-invasive smart pointers). Then, I can avoid memory fragmentation issues since class Foo move the objects around (and just update the corresponding Ptr). The only reason why this Foo moving objects around in non-invasive smart pointers being easier than invasive smart pointers is: In non-invasive smart pointers, there is only one pointer that points to each Foo. In invasive smart pointers, I have no idea how many objects point to each Foo. Now, the only cost of non-invasive smart pointers ... is the double indirection. [Perhaps this screws up the caches]. Does anyone have a good study of expensive this extra layer of indirection is?

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  • Passing a pointer to a function that doesn't match the requirements of the formal parameter

    - by Andreas Grech
    int valid (int x, int y) { return x + y; } int invalid (int x) { return x; } int func (int *f (int, int), int x, int y) { //f is a pointer to a function taking 2 ints and returning an int return f(x, y); } int main () { int val = func(valid, 1, 2), inval = func(invalid, 1, 2); // <- 'invalid' does not match the contract printf("Valid: %d\n", val); printf("Invalid: %d\n", inval); /* Output: * Valid: 3 * Invalid: 1 */ } At the line inval = func(invalid, 1, 2);, why am I not getting a compiler error? If func expects a pointer to a function taking 2 ints and I pass a pointer to a function that takes a single int, why isn't the compiler complaining? Also, since this is happening, what happens to the second parameter y in the invalid function?

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  • C++: How do I pass a function(without knowing its parameters) to another function?

    - by Ninja
    Hi all. I'm trying to create a function that will store and repeat another function given as a parameter for a specific amount of time or repeats given. But when you want to pass a function as a parameter you have to know all of its parameters before hand. How would I do if I wanted to pass the function as one parameter, and the parameters as another? void AddTimer(float time, int repeats, void (*func), params); // I know params has no type and that (*func) is missing parameters but it is just to show you what I mean Thanks in advance

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  • [PHP] function().function() VS function()function()

    - by kwokwai
    Hi all, I was writing a foreach Loop in PHP5. Here is the script: foreach(range('A','Z') as $char) // line 1 { // line 2 echo strtoupper($char)strtolower($char); // line 3 } // line 4 And I got this error message Parse error: parse error, unexpected T_STRING in testing.php on line 3 I spent almost an hour to figure out I should add a dot between two functions like this: echo strtoupper($char).strtolower($char); So I can't tell the difference between these two lines of codes: echo strtoupper($char).strtolower($char); echo strtoupper($char)strtolower($char);

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  • Using a pre-existing function for a new row

    - by Jonathan Kushner
    I have an Excel document that contains X columns and N number of rows. The very last column of a row performs a SUM of the first X-1 columns. The problem I have is, the user of this Excel document progressively adds rows to the document, and because of this, the function does not exist yet in the last column for new rows. I need a way to have this function exist in new rows dynamically (the user is not Excel-savvy and doesn't have the ability to just drag the function down a row).

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  • Error in running script [closed]

    - by SWEngineer
    I'm trying to run heathusf_v1.1.0.tar.gz found here I installed tcsh to make build_heathusf work. But, when I run ./build_heathusf, I get the following (I'm running that on a Fedora Linux system from Terminal): $ ./build_heathusf Compiling programs to build a library of image processing functions. convexpolyscan.c: In function ‘cdelete’: convexpolyscan.c:346:5: warning: incompatible implicit declaration of built-in function ‘bcopy’ [enabled by default] myalloc.c: In function ‘mycalloc’: myalloc.c:68:16: error: invalid storage class for function ‘store_link’ myalloc.c: In function ‘mymalloc’: myalloc.c:101:16: error: invalid storage class for function ‘store_link’ myalloc.c: In function ‘myfree’: myalloc.c:129:27: error: invalid storage class for function ‘find_link’ myalloc.c:131:12: warning: assignment makes pointer from integer without a cast [enabled by default] myalloc.c: At top level: myalloc.c:150:13: warning: conflicting types for ‘store_link’ [enabled by default] myalloc.c:150:13: error: static declaration of ‘store_link’ follows non-static declaration myalloc.c:91:4: note: previous implicit declaration of ‘store_link’ was here myalloc.c:164:24: error: conflicting types for ‘find_link’ myalloc.c:131:14: note: previous implicit declaration of ‘find_link’ was here Building the mammogram resizing program. gcc -O2 -I. -I../common mkimage.o -o mkimage -L../common -lmammo -lm ../common/libmammo.a(aggregate.o): In function `aggregate': aggregate.c:(.text+0x7fa): undefined reference to `mycalloc' aggregate.c:(.text+0x81c): undefined reference to `mycalloc' aggregate.c:(.text+0x868): undefined reference to `mycalloc' ../common/libmammo.a(aggregate.o): In function `aggregate_median': aggregate.c:(.text+0xbc5): undefined reference to `mymalloc' aggregate.c:(.text+0xbfb): undefined reference to `mycalloc' aggregate.c:(.text+0xc3c): undefined reference to `mycalloc' ../common/libmammo.a(aggregate.o): In function `aggregate': aggregate.c:(.text+0x9b5): undefined reference to `myfree' ../common/libmammo.a(aggregate.o): In function `aggregate_median': aggregate.c:(.text+0xd85): undefined reference to `myfree' ../common/libmammo.a(optical_density.o): In function `linear_optical_density': optical_density.c:(.text+0x29e): undefined reference to `mymalloc' optical_density.c:(.text+0x342): undefined reference to `mycalloc' optical_density.c:(.text+0x383): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `log10_optical_density': optical_density.c:(.text+0x693): undefined reference to `mymalloc' optical_density.c:(.text+0x74f): undefined reference to `mycalloc' optical_density.c:(.text+0x790): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `map_with_ushort_lut': optical_density.c:(.text+0xb2e): undefined reference to `mymalloc' optical_density.c:(.text+0xb87): undefined reference to `mycalloc' optical_density.c:(.text+0xbc6): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `linear_optical_density': optical_density.c:(.text+0x4d9): undefined reference to `myfree' ../common/libmammo.a(optical_density.o): In function `log10_optical_density': optical_density.c:(.text+0x8f1): undefined reference to `myfree' ../common/libmammo.a(optical_density.o): In function `map_with_ushort_lut': optical_density.c:(.text+0xd0d): undefined reference to `myfree' ../common/libmammo.a(virtual_image.o): In function `deallocate_cached_image': virtual_image.c:(.text+0x3dc6): undefined reference to `myfree' virtual_image.c:(.text+0x3dd7): undefined reference to `myfree' ../common/libmammo.a(virtual_image.o):virtual_image.c:(.text+0x3de5): more undefined references to `myfree' follow ../common/libmammo.a(virtual_image.o): In function `allocate_cached_image': virtual_image.c:(.text+0x4233): undefined reference to `mycalloc' virtual_image.c:(.text+0x4253): undefined reference to `mymalloc' virtual_image.c:(.text+0x4275): undefined reference to `mycalloc' virtual_image.c:(.text+0x42e7): undefined reference to `mycalloc' virtual_image.c:(.text+0x44f9): undefined reference to `mycalloc' virtual_image.c:(.text+0x47a9): undefined reference to `mycalloc' virtual_image.c:(.text+0x4a45): undefined reference to `mycalloc' virtual_image.c:(.text+0x4af4): undefined reference to `myfree' collect2: error: ld returned 1 exit status make: *** [mkimage] Error 1 Building the breast segmentation program. gcc -O2 -I. -I../common breastsegment.o segment.o -o breastsegment -L../common -lmammo -lm breastsegment.o: In function `render_segmentation_sketch': breastsegment.c:(.text+0x43): undefined reference to `mycalloc' breastsegment.c:(.text+0x58): undefined reference to `mycalloc' breastsegment.c:(.text+0x12f): undefined reference to `mycalloc' breastsegment.c:(.text+0x1b9): undefined reference to `myfree' breastsegment.c:(.text+0x1c6): undefined reference to `myfree' breastsegment.c:(.text+0x1e1): undefined reference to `myfree' segment.o: In function `find_center': segment.c:(.text+0x53): undefined reference to `mycalloc' segment.c:(.text+0x71): undefined reference to `mycalloc' segment.c:(.text+0x387): undefined reference to `myfree' segment.o: In function `bordercode': segment.c:(.text+0x4ac): undefined reference to `mycalloc' segment.c:(.text+0x546): undefined reference to `mycalloc' segment.c:(.text+0x651): undefined reference to `mycalloc' segment.c:(.text+0x691): undefined reference to `myfree' segment.o: In function `estimate_tissue_image': segment.c:(.text+0x10d4): undefined reference to `mycalloc' segment.c:(.text+0x14da): undefined reference to `mycalloc' segment.c:(.text+0x1698): undefined reference to `mycalloc' segment.c:(.text+0x1834): undefined reference to `mycalloc' segment.c:(.text+0x1850): undefined reference to `mycalloc' segment.o:segment.c:(.text+0x186a): more undefined references to `mycalloc' follow segment.o: In function `estimate_tissue_image': segment.c:(.text+0x1bbc): undefined reference to `myfree' segment.c:(.text+0x1c4a): undefined reference to `mycalloc' segment.c:(.text+0x1c7c): undefined reference to `mycalloc' segment.c:(.text+0x1d8e): undefined reference to `myfree' segment.c:(.text+0x1d9b): undefined reference to `myfree' segment.c:(.text+0x1da8): undefined reference to `myfree' segment.c:(.text+0x1dba): undefined reference to `myfree' segment.c:(.text+0x1dc9): undefined reference to `myfree' segment.o:segment.c:(.text+0x1dd8): more undefined references to `myfree' follow segment.o: In function `estimate_tissue_image': segment.c:(.text+0x20bf): undefined reference to `mycalloc' segment.o: In function `segment_breast': segment.c:(.text+0x24cd): undefined reference to `mycalloc' segment.o: In function `find_center': segment.c:(.text+0x3a4): undefined reference to `myfree' segment.o: In function `bordercode': segment.c:(.text+0x6ac): undefined reference to `myfree' ../common/libmammo.a(aggregate.o): In function `aggregate': aggregate.c:(.text+0x7fa): undefined reference to `mycalloc' aggregate.c:(.text+0x81c): undefined reference to `mycalloc' aggregate.c:(.text+0x868): undefined reference to `mycalloc' ../common/libmammo.a(aggregate.o): In function `aggregate_median': aggregate.c:(.text+0xbc5): undefined reference to `mymalloc' aggregate.c:(.text+0xbfb): undefined reference to `mycalloc' aggregate.c:(.text+0xc3c): undefined reference to `mycalloc' ../common/libmammo.a(aggregate.o): In function `aggregate': aggregate.c:(.text+0x9b5): undefined reference to `myfree' ../common/libmammo.a(aggregate.o): In function `aggregate_median': aggregate.c:(.text+0xd85): undefined reference to `myfree' ../common/libmammo.a(cc_label.o): In function `cc_label': cc_label.c:(.text+0x20c): undefined reference to `mycalloc' cc_label.c:(.text+0x6c2): undefined reference to `mycalloc' cc_label.c:(.text+0xbaa): undefined reference to `myfree' ../common/libmammo.a(cc_label.o): In function `cc_label_0bkgd': cc_label.c:(.text+0xe17): undefined reference to `mycalloc' cc_label.c:(.text+0x12d7): undefined reference to `mycalloc' cc_label.c:(.text+0x17e7): undefined reference to `myfree' ../common/libmammo.a(cc_label.o): In function `cc_relabel_by_intensity': cc_label.c:(.text+0x18c5): undefined reference to `mycalloc' ../common/libmammo.a(cc_label.o): In function `cc_label_4connect': cc_label.c:(.text+0x1cf0): undefined reference to `mycalloc' cc_label.c:(.text+0x2195): undefined reference to `mycalloc' cc_label.c:(.text+0x26a4): undefined reference to `myfree' ../common/libmammo.a(cc_label.o): In function `cc_relabel_by_intensity': cc_label.c:(.text+0x1b06): undefined reference to `myfree' ../common/libmammo.a(convexpolyscan.o): In function `polyscan_coords': convexpolyscan.c:(.text+0x6f0): undefined reference to `mycalloc' convexpolyscan.c:(.text+0x75f): undefined reference to `mycalloc' convexpolyscan.c:(.text+0x7ab): undefined reference to `myfree' convexpolyscan.c:(.text+0x7b8): undefined reference to `myfree' ../common/libmammo.a(convexpolyscan.o): In function `polyscan_poly_cacheim': convexpolyscan.c:(.text+0x805): undefined reference to `mycalloc' convexpolyscan.c:(.text+0x894): undefined reference to `myfree' ../common/libmammo.a(mikesfileio.o): In function `read_segmentation_file': mikesfileio.c:(.text+0x1e9): undefined reference to `mycalloc' mikesfileio.c:(.text+0x205): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `linear_optical_density': optical_density.c:(.text+0x29e): undefined reference to `mymalloc' optical_density.c:(.text+0x342): undefined reference to `mycalloc' optical_density.c:(.text+0x383): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `log10_optical_density': optical_density.c:(.text+0x693): undefined reference to `mymalloc' optical_density.c:(.text+0x74f): undefined reference to `mycalloc' optical_density.c:(.text+0x790): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `map_with_ushort_lut': optical_density.c:(.text+0xb2e): undefined reference to `mymalloc' optical_density.c:(.text+0xb87): undefined reference to `mycalloc' optical_density.c:(.text+0xbc6): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `linear_optical_density': optical_density.c:(.text+0x4d9): undefined reference to `myfree' ../common/libmammo.a(optical_density.o): In function `log10_optical_density': optical_density.c:(.text+0x8f1): undefined reference to `myfree' ../common/libmammo.a(optical_density.o): In function `map_with_ushort_lut': optical_density.c:(.text+0xd0d): undefined reference to `myfree' ../common/libmammo.a(virtual_image.o): In function `deallocate_cached_image': virtual_image.c:(.text+0x3dc6): undefined reference to `myfree' virtual_image.c:(.text+0x3dd7): undefined reference to `myfree' ../common/libmammo.a(virtual_image.o):virtual_image.c:(.text+0x3de5): more undefined references to `myfree' follow ../common/libmammo.a(virtual_image.o): In function `allocate_cached_image': virtual_image.c:(.text+0x4233): undefined reference to `mycalloc' virtual_image.c:(.text+0x4253): undefined reference to `mymalloc' virtual_image.c:(.text+0x4275): undefined reference to `mycalloc' virtual_image.c:(.text+0x42e7): undefined reference to `mycalloc' virtual_image.c:(.text+0x44f9): undefined reference to `mycalloc' virtual_image.c:(.text+0x47a9): undefined reference to `mycalloc' virtual_image.c:(.text+0x4a45): undefined reference to `mycalloc' virtual_image.c:(.text+0x4af4): undefined reference to `myfree' collect2: error: ld returned 1 exit status make: *** [breastsegment] Error 1 Building the mass feature generation program. gcc -O2 -I. -I../common afumfeature.o -o afumfeature -L../common -lmammo -lm afumfeature.o: In function `afum_process': afumfeature.c:(.text+0xd80): undefined reference to `mycalloc' afumfeature.c:(.text+0xd9c): undefined reference to `mycalloc' afumfeature.c:(.text+0xe80): undefined reference to `mycalloc' afumfeature.c:(.text+0x11f8): undefined reference to `myfree' afumfeature.c:(.text+0x1207): undefined reference to `myfree' afumfeature.c:(.text+0x1214): undefined reference to `myfree' ../common/libmammo.a(aggregate.o): In function `aggregate': aggregate.c:(.text+0x7fa): undefined reference to `mycalloc' aggregate.c:(.text+0x81c): undefined reference to `mycalloc' aggregate.c:(.text+0x868): undefined reference to `mycalloc' ../common/libmammo.a(aggregate.o): In function `aggregate_median': aggregate.c:(.text+0xbc5): undefined reference to `mymalloc' aggregate.c:(.text+0xbfb): undefined reference to `mycalloc' aggregate.c:(.text+0xc3c): undefined reference to `mycalloc' ../common/libmammo.a(aggregate.o): In function `aggregate': aggregate.c:(.text+0x9b5): undefined reference to `myfree' ../common/libmammo.a(aggregate.o): In function `aggregate_median': aggregate.c:(.text+0xd85): undefined reference to `myfree' ../common/libmammo.a(convexpolyscan.o): In function `polyscan_coords': convexpolyscan.c:(.text+0x6f0): undefined reference to `mycalloc' convexpolyscan.c:(.text+0x75f): undefined reference to `mycalloc' convexpolyscan.c:(.text+0x7ab): undefined reference to `myfree' convexpolyscan.c:(.text+0x7b8): undefined reference to `myfree' ../common/libmammo.a(convexpolyscan.o): In function `polyscan_poly_cacheim': convexpolyscan.c:(.text+0x805): undefined reference to `mycalloc' convexpolyscan.c:(.text+0x894): undefined reference to `myfree' ../common/libmammo.a(mikesfileio.o): In function `read_segmentation_file': mikesfileio.c:(.text+0x1e9): undefined reference to `mycalloc' mikesfileio.c:(.text+0x205): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `linear_optical_density': optical_density.c:(.text+0x29e): undefined reference to `mymalloc' optical_density.c:(.text+0x342): undefined reference to `mycalloc' optical_density.c:(.text+0x383): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `log10_optical_density': optical_density.c:(.text+0x693): undefined reference to `mymalloc' optical_density.c:(.text+0x74f): undefined reference to `mycalloc' optical_density.c:(.text+0x790): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `map_with_ushort_lut': optical_density.c:(.text+0xb2e): undefined reference to `mymalloc' optical_density.c:(.text+0xb87): undefined reference to `mycalloc' optical_density.c:(.text+0xbc6): undefined reference to `mycalloc' ../common/libmammo.a(optical_density.o): In function `linear_optical_density': optical_density.c:(.text+0x4d9): undefined reference to `myfree' ../common/libmammo.a(optical_density.o): In function `log10_optical_density': optical_density.c:(.text+0x8f1): undefined reference to `myfree' ../common/libmammo.a(optical_density.o): In function `map_with_ushort_lut': optical_density.c:(.text+0xd0d): undefined reference to `myfree' ../common/libmammo.a(virtual_image.o): In function `deallocate_cached_image': virtual_image.c:(.text+0x3dc6): undefined reference to `myfree' virtual_image.c:(.text+0x3dd7): undefined reference to `myfree' ../common/libmammo.a(virtual_image.o):virtual_image.c:(.text+0x3de5): more undefined references to `myfree' follow ../common/libmammo.a(virtual_image.o): In function `allocate_cached_image': virtual_image.c:(.text+0x4233): undefined reference to `mycalloc' virtual_image.c:(.text+0x4253): undefined reference to `mymalloc' virtual_image.c:(.text+0x4275): undefined reference to `mycalloc' virtual_image.c:(.text+0x42e7): undefined reference to `mycalloc' virtual_image.c:(.text+0x44f9): undefined reference to `mycalloc' virtual_image.c:(.text+0x47a9): undefined reference to `mycalloc' virtual_image.c:(.text+0x4a45): undefined reference to `mycalloc' virtual_image.c:(.text+0x4af4): undefined reference to `myfree' collect2: error: ld returned 1 exit status make: *** [afumfeature] Error 1 Building the mass detection program. make: Nothing to be done for `all'. Building the performance evaluation program. gcc -O2 -I. -I../common DDSMeval.o polyscan.o -o DDSMeval -L../common -lmammo -lm ../common/libmammo.a(mikesfileio.o): In function `read_segmentation_file': mikesfileio.c:(.text+0x1e9): undefined reference to `mycalloc' mikesfileio.c:(.text+0x205): undefined reference to `mycalloc' collect2: error: ld returned 1 exit status make: *** [DDSMeval] Error 1 Building the template creation program. gcc -O2 -I. -I../common mktemplate.o polyscan.o -o mktemplate -L../common -lmammo -lm Building the drawimage program. gcc -O2 -I. -I../common drawimage.o -o drawimage -L../common -lmammo -lm ../common/libmammo.a(mikesfileio.o): In function `read_segmentation_file': mikesfileio.c:(.text+0x1e9): undefined reference to `mycalloc' mikesfileio.c:(.text+0x205): undefined reference to `mycalloc' collect2: error: ld returned 1 exit status make: *** [drawimage] Error 1 Building the compression/decompression program jpeg. gcc -O2 -DSYSV -DNOTRUNCATE -c lexer.c lexer.c:41:1: error: initializer element is not constant lexer.c:41:1: error: (near initialization for ‘yyin’) lexer.c:41:1: error: initializer element is not constant lexer.c:41:1: error: (near initialization for ‘yyout’) lexer.c: In function ‘initparser’: lexer.c:387:21: warning: incompatible implicit declaration of built-in function ‘strlen’ [enabled by default] lexer.c: In function ‘MakeLink’: lexer.c:443:16: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] lexer.c:447:7: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:452:7: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:455:34: warning: incompatible implicit declaration of built-in function ‘calloc’ [enabled by default] lexer.c:458:7: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:460:3: warning: incompatible implicit declaration of built-in function ‘strcpy’ [enabled by default] lexer.c: In function ‘getstr’: lexer.c:548:26: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] lexer.c:552:4: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:557:21: warning: incompatible implicit declaration of built-in function ‘calloc’ [enabled by default] lexer.c:557:28: warning: incompatible implicit declaration of built-in function ‘strlen’ [enabled by default] lexer.c:561:7: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c: In function ‘parser’: lexer.c:794:21: warning: incompatible implicit declaration of built-in function ‘calloc’ [enabled by default] lexer.c:798:8: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:1074:21: warning: incompatible implicit declaration of built-in function ‘calloc’ [enabled by default] lexer.c:1078:8: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:1116:21: warning: incompatible implicit declaration of built-in function ‘calloc’ [enabled by default] lexer.c:1120:8: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:1154:25: warning: incompatible implicit declaration of built-in function ‘calloc’ [enabled by default] lexer.c:1158:5: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:1190:5: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:1247:25: warning: incompatible implicit declaration of built-in function ‘calloc’ [enabled by default] lexer.c:1251:5: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c:1283:5: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default] lexer.c: In function ‘yylook’: lexer.c:1867:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] lexer.c:1867:20: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] lexer.c:1877:12: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] lexer.c:1877:23: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] make: *** [lexer.o] Error 1

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  • C Programming: malloc() inside another function

    - by vikramtheone
    Hi Guys, I need help with malloc() inside another function. I'm passing a pointer and size to the function from my main() and I would like to allocate memory for that pointer dynamically using malloc() from inside that called function, but what I see is that.... the memory which is getting allocated is for the pointer declared withing my called function and not for the pointer which is inside the main(). How should I pass a pointer to a function and allocate memory for the passed pointer from inside the called function? Can anyone throw light on this? Help!!! Vikram I have written the following code and I get the output as shown below SOURCE: main() { unsigned char *input_image; unsigned int bmp_image_size = 262144; if(alloc_pixels(input_image, bmp_image_size)==NULL) printf("\nPoint2: Memory allocated: %d bytes",_msize(input_image)); else printf("\nPoint3: Memory not allocated"); } signed char alloc_pixels(unsigned char *ptr, unsigned int size) { signed char status = NO_ERROR; ptr = NULL; ptr = (unsigned char*)malloc(size); if(ptr== NULL) { status = ERROR; free(ptr); printf("\nERROR: Memory allocation did not complete successfully!"); } printf("\nPoint1: Memory allocated: %d bytes",_msize(ptr)); return status; } PROGRAM OUTPUT: Point1: Memory allocated ptr: 262144 bytes Point2: Memory allocated input_image: 0 bytes

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  • What is the merit of the "function" type (not "pointer to function")

    - by anatolyg
    Reading the C++ Standard, i see that there are "function" types and "pointer to function" types: typedef int func(int); // function typedef int (*pfunc)(int); // pointer to function typedef func* pfunc; // same as above I have never seen the function types used outside of examples (or maybe i didn't recognize their usage?). Some examples: func increase, decrease; // declares two functions int increase(int), decrease(int); // same as above int increase(int x) {return x + 1;} // cannot use the typedef when defining functions int decrease(int x) {return x - 1;} // cannot use the typedef when defining functions struct mystruct { func add, subtract, multiply; // declares three member functions int member; }; int mystruct::add(int x) {return x + member;} // cannot use the typedef int mystruct::subtract(int x) {return x - member;} int main() { func k; // the syntax is correct but the variable k is useless! mystruct myobject; myobject.member = 4; cout << increase(5) << ' ' << decrease(5) << '\n'; // outputs 6 and 4 cout << myobject.add(5) << ' ' << myobject.subtract(5) << '\n'; // 9 and 1 } Seeing that the function types support syntax that doesn't appear in C (declaring member functions), i guess they are not just a part of C baggage that C++ has to support for backward compatibility. So is there any use for function types, other than demonstrating some funky syntax?

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  • Function lfit in numerical recipes, providing a test function

    - by Simon Walker
    Hi I am trying to fit collected data to a polynomial equation and I found the lfit function from Numerical Recipes. I only have access to the second edition, so am using that. I have read about the lfit function and its parameters, one of which is a function pointer, given in the documentation as void (*funcs)(float, float [], int)) with the help The user supplies a routine funcs(x,afunc,ma) that returns the ma basis functions evaluated at x = x in the array afunc[1..ma]. I am struggling to understand how this lfit function works. An example function I found is given below: void fpoly(float x, float p[], int np) /*Fitting routine for a polynomial of degree np-1, with coe?cients in the array p[1..np].*/ { int j; p[1]=1.0; for (j=2;j<=np;j++) p[j]=p[j-1]*x; } When I run through the source code for the lfit function in gdb I can see no reference to the funcs pointer. When I try and fit a simple data set with the function, I get the following error message. Numerical Recipes run-time error... gaussj: Singular Matrix ...now exiting to system... Clearly somehow a matrix is getting defined with all zeroes. I am going to involve this function fitting in a large loop so using another language is not really an option. Hence why I am planning on using C/C++. For reference, the test program is given here: int main() { float x[5] = {0., 0., 1., 2., 3.}; float y[5] = {0., 0., 1.2, 3.9, 7.5}; float sig[5] = {1., 1., 1., 1., 1.}; int ndat = 4; int ma = 4; /* parameters in equation */ float a[5] = {1, 1, 1, 0.1, 1.5}; int ia[5] = {1, 1, 1, 1, 1}; float **covar = matrix(1, ma, 1, ma); float chisq = 0; lfit(x,y,sig,ndat,a,ia,ma,covar,&chisq,fpoly); printf("%f\n", chisq); free_matrix(covar, 1, ma, 1, ma); return 0; } Also confusing the issue, all the Numerical Recipes functions are 1 array-indexed so if anyone has corrections to my array declarations let me know also! Cheers

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  • Performance question: Inverting an array of pointers in-place vs array of values

    - by Anders
    The background for asking this question is that I am solving a linearized equation system (Ax=b), where A is a matrix (typically of dimension less than 100x100) and x and b are vectors. I am using a direct method, meaning that I first invert A, then find the solution by x=A^(-1)b. This step is repated in an iterative process until convergence. The way I'm doing it now, using a matrix library (MTL4): For every iteration I copy all coeffiecients of A (values) in to the matrix object, then invert. This the easiest and safest option. Using an array of pointers instead: For my particular case, the coefficients of A happen to be updated between each iteration. These coefficients are stored in different variables (some are arrays, some are not). Would there be a potential for performance gain if I set up A as an array containing pointers to these coefficient variables, then inverting A in-place? The nice thing about the last option is that once I have set up the pointers in A before the first iteration, I would not need to copy any values between successive iterations. The values which are pointed to in A would automatically be updated between iterations. So the performance question boils down to this, as I see it: - The matrix inversion process takes roughly the same amount of time, assuming de-referencing of pointers is non-expensive. - The array of pointers does not need the extra memory for matrix A containing values. - The array of pointers option does not have to copy all NxN values of A between each iteration. - The values that are pointed to the array of pointers option are generally NOT ordered in memory. Hopefully, all values lie relatively close in memory, but *A[0][1] is generally not next to *A[0][0] etc. Any comments to this? Will the last remark affect performance negatively, thus weighing up for the positive performance effects?

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  • Get Function Pointer to function in a shared library I didn't directly load

    - by bdk
    My Linux application (A) links against a Third Party shared Library (B) which I don't have source code to. This library makes use of another third party shared library that I don't have source code to (C). I believe that (B) uses dlopen to access (C) instead of directly linking. My reasoning for this is that 'ldd' on (B) does not show (C) and objdump -X (B) shows references to dlopen/dlclose/dlsym. My requirement is that I need to in my code for (A) get a function pointer to a function foo() located in (C). Normally I'd use dlsym for this, but I need to pass it the handle returned from dlopen which I don't have since (B) does not expose this. - For the larger context: I need to modify the function in (C) such that everytime it calls its helper function bar() (also located in (C)), it also calls a function with the same signature located in (A) with the same parameters (Basically inject my code into the codepath of (C) foo()-bar(). I believe I've found a way to accomplish this using gdb, but in order to port my gdb command list, but I'm stuck on the step of getting the function pointer. I'm also open to alternatives to accomplish the same task rather than the exact problem as stated above Edit: After writing this I realized I can probably just do another dlopen on the file in my code and the symbols returned via dlsym on that handle should be the same as received via the original dlopen, If I'm reading the dlopen man page correctly. However I'm still interested in advice or assistance with the my larger context, If theres a better way to go about this

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  • How to pass a function in a function?

    - by SoulBeaver
    That's an odd title. I would greatly appreciate it if somebody could clarify what exactly I'm asking because I'm not so sure myself. I'm watching the Stanford videos on Programming Paradigms(that teacher is awesome) and I'm up to video five when he started doing this: void *lSearch( void* key, void* base, int elemSize, int n, int (*cmpFn)(void*, void*)) Naturally, I thought to myself, "Oi, I didn't know you could declare a function and define it later!". So I created my own C++ test version. int foo(int (*bar)(void*, void*)); int bar(void* a, void* b); int main(int argc, char** argv) { int *func = 0; foo(bar); cin.get(); return 0; } int foo(int (*bar)(void*, void*)) { int c(10), d(15); int *a = &c; int *b = &d; bar(a, b); return 0; } int bar(void* a, void* b) { cout << "Why hello there." << endl; return 0; } The question about the code is this: it fails if I declare function int *bar as a parameter of foo, but not int (*bar). Why!? Also, the video confuses me in the fact that his lSearch definition void* lSearch( /*params*/ , int (*cmpFn)(void*, void*)) is calling cmpFn in the definition, but when calling the lSearch function lSearch( /*params*/, intCmp ); also calls the defined function int intCmp(void* elem1, void* elem2); and I don't get how that works. Why, in lSearch, is the function called cmpFn, but defined as intCmp, which is of type int, not int* and still works? And why does the function in lSearch not have to have defined parameters?

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  • SQL SERVER – Introduction to Function SIGN

    - by pinaldave
    Yesterday I received an email from a friend asking how do SIGN function works. Well SIGN Function is very fundamental function. It will return the value 1, -1 or 0. If your value is negative it will return you negative -1 and if it is positive it will return you positive +1. Let us start with a simple small example. DECLARE @IntVal1 INT, @IntVal2 INT,@IntVal3 INT DECLARE @NumVal1 DECIMAL(4,2), @NumVal2 DECIMAL(4,2),@NumVal3 DECIMAL(4,2) SET @IntVal1 = 9; SET @IntVal2 = -9; SET @IntVal3 = 0; SET @NumVal1 = 9.0; SET @NumVal2 = -9.0; SET @NumVal3 = 0.0; SELECT SIGN(@IntVal1) IntVal1,SIGN(@IntVal2) IntVal2,SIGN(@IntVal3) IntVal3 SELECT SIGN(@NumVal1) NumVal1,SIGN(@NumVal2) NumVal2,SIGN(@NumVal2) NumVal3   The above function will give us following result set. You will notice that when there is positive value the function gives positive values and if the values are negative it will return you negative values. Also you will notice that if the data type is  INT the return value is INT and when the value passed to the function is Numeric the result also matches it. Not every datatype is compatible with this function.  Here is the quick look up of the return types. bigint -> bigint int/smallint/tinyint -> int money/smallmoney -> money numeric/decimal -> numeric/decimal everybody else -> float What will be the best example of the usage of this function that you will not have to use the CASE Statement. Here is example of CASE Statement usage and the same replaced with SIGN function. USE tempdb GO CREATE TABLE TestTable (Date1 SMALLDATETIME, Date2 SMALLDATETIME) INSERT INTO TestTable (Date1, Date2) SELECT '2012-06-22 16:15', '2012-06-20 16:15' UNION ALL SELECT '2012-06-24 16:15', '2012-06-22 16:15' UNION ALL SELECT '2012-06-22 16:15', '2012-06-22 16:15' GO -- Using Case Statement SELECT CASE WHEN DATEDIFF(d,Date1,Date2) > 0 THEN 1 WHEN DATEDIFF(d,Date1,Date2) < 0 THEN -1 ELSE 0 END AS Col FROM TestTable GO -- Using SIGN Function SELECT SIGN(DATEDIFF(d,Date1,Date2)) AS Col FROM TestTable GO DROP TABLE TestTable GO This was interesting blog post for me to write. Let me know your opinion. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Passing an array of an array of char to a function

    - by L.A. Rabida
    In my program, I may need to load a large file, but not always. So I have defined: char** largefilecontents; string fileName="large.txt"; When I need to load the file, the program calles this function: bool isitok=LoadLargeFile(fileName,largefilecontents); And the function is: bool LoadLargeFile(string &filename, char ** &lines) { if (lines) delete [] lines; ifstream largeFile; #ifdef LINUX largeFile.open(filename.c_str()); #endif #ifdef WINDOWS largeFile.open(filename.c_str(),ios::binary); #endif if (!largeFile.is_open()) return false; lines=new char *[10000]; if (!lines) return false; largeFile.clear(); largeFile.seekg(ios::beg); for (int i=0; i>-1; i++) { string line=""; getline(largeFile,line); if (largeFile.tellg()==-1) break; //when end of file is reached, tellg returns -1 lines[i]=new char[line.length()]; lines[i]=const_cast<char*>(line.c_str()); cout << lines[i] << endl; //debug output } return true; } When I view the debug output of this function, "cout << lines[i] << endl;", it is fine. But when I then check this in the main program like this, it is all messed up: for (i=0; i<10000; i++) cout << largefilecontents[i] << endl; So within the function LoadLargeFile(), the results are fine, but without LoadLargeFile(), the results are all messed up. My guess is that the char ** &lines part of the function isn't right, but I do not know what this should be. Could someone help me? Thank you in advance!

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  • Which languages support *recursive* function literals / anonymous functions?

    - by Hugh Allen
    It seems quite a few mainstream languages support function literals these days. They are also called anonymous functions, but I don't care if they have a name. The important thing is that a function literal is an expression which yields a function which hasn't already been defined elsewhere, so for example in C, &printf doesn't count. EDIT to add: if you have a genuine function literal expression <exp>, you should be able to pass it to a function f(<exp>) or immediately apply it to an argument, ie. <exp>(5). I'm curious which languages let you write function literals which are recursive. Wikipedia's "anonymous recursion" article doesn't give any programming examples. Let's use the recursive factorial function as the example. Here are the ones I know: JavaScript / ECMAScript can do it with callee: function(n){if (n<2) {return 1;} else {return n * arguments.callee(n-1);}} it's easy in languages with letrec, eg Haskell (which calls it let): let fac x = if x<2 then 1 else fac (x-1) * x in fac and there are equivalents in Lisp and Scheme. Note that the binding of fac is local to the expression, so the whole expression is in fact an anonymous function. Are there any others?

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  • How to get rid of void-pointers.

    - by Patrick
    I inherited a big application that was originally written in C (but in the mean time a lot of C++ was also added to it). Because of historical reasons, the application contains a lot of void-pointers. Before you start to choke, let me explain why this was done. The application contains many different data structures, but they are stored in 'generic' containers. Nowadays I would use templated STL containers for it, or I would give all data structures a common base class, so that the container can store pointers to the base class, but in the [good?] old C days, the only solution was to cast the struct-pointer to a void-pointer. Additionally, there is a lot of code that works on these void-pointers, and uses very strange C constructions to emulate polymorphism in C. I am now reworking the application, and trying to get rid of the void-pointers. Adding a common base-class to all the data structures isn't that hard (few days of work), but the problem is that the code is full of constructions like shown below. This is an example of how data is stored: void storeData (int datatype, void *data); // function prototype ... Customer *myCustomer = ...; storeData (TYPE_CUSTOMER, myCustomer); This is an example of how data is fetched again: Customer *myCustomer = (Customer *) fetchData (int datatype, char *key); I actually want to replace all the void-pointers with some smart-pointer (reference-counted), but I can't find a trick to automate (or at least) help me to get rid of all the casts to and from void-pointers. Any tips on how to find, replace, or interact in any possible way with these conversions?

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  • Javascript: Calling a function written in an anonymous function from String with the function's name

    - by Kai barry yuzanic
    Hello. I've started using jQuery and am wondering how to call functions in an anonymous function dynamically from String. Let's say for instance, I have the following functions: function foo() { // Being in the global namespace, // this function can be called with window['foo']() alert("foo"); } jQuery(document).ready(function(){ function bar() { // How can this function be called // by using a String of the function's name 'bar'?? alert("bar"); } // I want to call the function bar here from String with the name 'bar' } I've been trying to figure out what could be the counterpart of 'window', which can call functions from the global namespace such as window["foo"]. In the small example above, how I can call the function bar from a String "bar"? Thank you for your help.

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