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  • LibPCL issues on Ubuntu 13.10

    - by user254885
    i wanted to install the Point Cloud Library but it does not work i use an ODROID board(ARM processor) Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: libpcl-all : Depends: libpcl-1.7-all but it is not going to be installed E: Unable to correct problems, you have held broken packages. by compiling v1.7 , i get these errors : /usr/lib/gcc/arm-linux-gnueabihf/4.8/../../../arm-linux-gnueabihf/libpthread.a(ptw-fcntl.o): In function `__fcntl_nocancel': /build/buildd/eglibc-2.17/nptl/../sysdeps/unix/sysv/linux/i386/fcntl.c:37: undefined reference to `__libc_do_syscall' /usr/lib/gcc/arm-linux-gnueabihf/4.8/../../../arm-linux-gnueabihf/libpthread.a(ptw-fcntl.o): In function `__libc_fcntl': /build/buildd/eglibc-2.17/nptl/../sysdeps/unix/sysv/linux/i386/fcntl.c:53: undefined reference to `__libc_do_syscall' /build/buildd/eglibc-2.17/nptl/../sysdeps/unix/sysv/linux/i386/fcntl.c:57: undefined reference to `__libc_do_syscall' /usr/lib/gcc/arm-linux-gnueabihf/4.8/../../../arm-linux-gnueabihf/libpthread.a(ptw-open64.o): In function `__libc_open64': /build/buildd/eglibc-2.17/nptl/../sysdeps/unix/sysv/linux/open64.c:41: undefined reference to `__libc_do_syscall' /build/buildd/eglibc-2.17/nptl/../sysdeps/unix/sysv/linux/open64.c:45: undefined reference to `__libc_do_syscall' /usr/lib/gcc/arm-linux-gnueabihf/4.8/../../../arm-linux-gnueabihf/libpthread.a(cancellation.o):/build/buildd/eglibc-2.17/nptl/cancellation.c:96: more undefined references to `__libc_do_syscall' follow collect2: error: ld returned 1 exit status make[2]: *** [bin/pcl_convert_pcd_ascii_binary] Error 1 make[1]: *** [io/tools/CMakeFiles/pcl_convert_pcd_ascii_binary.dir/all] Error 2 make: *** [all] Error 2 i could not find anything in google to solve these errors i believe some packages were not ported for ARM processors any help would be appreciated $ dpkg --list | grep headers ii linux-headers-3.0.63-odroidx2 20130215 ii linux-headers-3.0.71-odroidx2 20130415 ii linux-headers-3.0.74-odroidx2 20130417 ii linux-headers-3.0.75-odroidx2 20130426 ii linux-headers-3.1.10-6 3.1.10-6.10 ii linux-headers-3.1.10-6-ac100 3.1.10-6.10 ii linux-headers-ac100 3.1.10.6.2 installing packages did'nt do well sudo apt-get install linux-generic [sudo] password for odroid: Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: debugedit libasound2-dev libestools2.1-dev librpmbuild3 librpmsign1 thunderbird-locale-en thunderbird-locale-en-gb thunderbird-locale-en-us thunderbird-locale-ko Use 'apt-get autoremove' to remove them. The following extra packages will be installed: linux-headers-3.11.0-17 linux-headers-3.11.0-17-generic linux-headers-generic linux-image-3.11.0-17-generic linux-image-generic Suggested packages: fdutils linux-doc-3.11.0 linux-source-3.11.0 linux-tools The following NEW packages will be installed: linux-generic linux-headers-3.11.0-17 linux-headers-3.11.0-17-generic linux-headers-generic linux-image-3.11.0-17-generic linux-image-generic 0 upgraded, 6 newly installed, 0 to remove and 0 not upgraded. Need to get 58.2 MB of archives. After this operation, 203 MB of additional disk space will be used. Do you want to continue [Y/n]? y Get:1 http://ports.ubuntu.com/ubuntu-ports/ saucy-updates/main linux-image-3.11.0-17-generic armhf 3.11.0-17.31 [44.5 MB] Get:2 http://ports.ubuntu.com/ubuntu-ports/ saucy-updates/main linux-image-generic armhf 3.11.0.17.18 [2,356 B] Get:3 http://ports.ubuntu.com/ubuntu-ports/ saucy-updates/main linux-headers-3.11.0-17 all 3.11.0-17.31 [12.6 MB] Get:4 http://ports.ubuntu.com/ubuntu-ports/ saucy-updates/main linux-headers-3.11.0-17-generic armhf 3.11.0-17.31 [1,128 kB] Get:5 http://ports.ubuntu.com/ubuntu-ports/ saucy-updates/main linux-headers-generic armhf 3.11.0.17.18 [2,350 B] Get:6 http://ports.ubuntu.com/ubuntu-ports/ saucy-updates/main linux-generic armhf 3.11.0.17.18 [1,726 B] Fetched 58.2 MB in 13s (4,379 kB/s) Selecting previously unselected package linux-image-3.11.0-17-generic. (Reading database ... 258618 files and directories currently installed.) Unpacking linux-image-3.11.0-17-generic (from .../linux-image-3.11.0-17-generic_3.11.0-17.31_armhf.deb) ... Examining /etc/kernel/preinst.d/ Done. Selecting previously unselected package linux-image-generic. Unpacking linux-image-generic (from .../linux-image-generic_3.11.0.17.18_armhf.deb) ... Selecting previously unselected package linux-headers-3.11.0-17. Unpacking linux-headers-3.11.0-17 (from .../linux-headers-3.11.0-17_3.11.0-17.31_all.deb) ... Selecting previously unselected package linux-headers-3.11.0-17-generic. Unpacking linux-headers-3.11.0-17-generic (from .../linux-headers-3.11.0-17-generic_3.11.0-17.31_armhf.deb) ... Selecting previously unselected package linux-headers-generic. Unpacking linux-headers-generic (from .../linux-headers-generic_3.11.0.17.18_armhf.deb) ... Selecting previously unselected package linux-generic. Unpacking linux-generic (from .../linux-generic_3.11.0.17.18_armhf.deb) ... Setting up linux-image-3.11.0-17-generic (3.11.0-17.31) ... Running depmod. update-initramfs: deferring update (hook will be called later) cp: cannot stat ‘/boot/initrd.img-3.11.0-17-generic’: No such file or directory Failed to copy /boot/initrd.img-3.11.0-17-generic to /boot/initrd.img at /var/lib/dpkg/info/linux-image-3.11.0-17-generic.postinst line 730. dpkg: error processing linux-image-3.11.0-17-generic (--configure): subprocess installed post-installation script returned error exit status 2 dpkg: dependency problems prevent configuration of linux-image-generic: linux-image-generic depends on linux-image-3.11.0-17-generic; however: Package linux-image-3.11.0-17-generic is not configured yet. dpkg: error processing linux-image-generic (--configure): dependency problems - leaving unconfigured Setting up linux-headers-3.11.0-17 (3.11.0-17.31) ... No apport report written because MaxReports is reached already No apport report written because MaxReports is reached already Setting up linux-headers-3.11.0-17-generic (3.11.0-17.31) ... Examining /etc/kernel/header_postinst.d. Setting up linux-headers-generic (3.11.0.17.18) ... dpkg: dependency problems prevent configuration of linux-generic: linux-generic depends on linux-image-generic (= 3.11.0.17.18); however: Package linux-image-generic is not configured yet. dpkg: error processing linux-generic (--configure): dependency problems - leaving unconfigured No apport report written because MaxReports is reached already Errors were encountered while processing: linux-image-3.11.0-17-generic linux-image-generic linux-generic E: Sub-process /usr/bin/dpkg returned an error code (1) i had to uninstall these cos they were messing up other packages installation(buildessentials were already installed)

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  • active record relations – who needs it?

    - by M2_
    Well, I`m confused about rails queries. For example: Affiche belongs_to :place Place has_many :affiches We can do this now: @affiches = Affiche.all( :joins => :place ) or @affiches = Affiche.all( :include => :place ) and we will get a lot of extra SELECTs, if there are many affiches: Place Load (0.2ms) SELECT "places".* FROM "places" WHERE "places"."id" = 3 LIMIT 1 Place Load (0.3ms) SELECT "places".* FROM "places" WHERE "places"."id" = 3 LIMIT 1 Place Load (0.8ms) SELECT "places".* FROM "places" WHERE "places"."id" = 444 LIMIT 1 Place Load (1.0ms) SELECT "places".* FROM "places" WHERE "places"."id" = 222 LIMIT 1 ...and so on... And (sic!) with :joins used every SELECT is doubled! Technically we cloud just write like this: @affiches = Affiche.all( ) and the result is totally the same! (Because we have relations declared). The wayout of keeping all data in one query is removing the relations and writing a big string with "LEFT OUTER JOIN", but still there is a problem of grouping data in multy-dimentional array and a problem of similar column names, such as id. What is done wrong? Or what am I doing wrong? UPDATE: Well, i have that string Place Load (2.5ms) SELECT "places".* FROM "places" WHERE ("places"."id" IN (3,444,222,57,663,32,154,20)) and a list of selects one by one id. Strange, but I get these separate selects when I`m doing this in each scope: <%= link_to a.place.name, **a.place**( :id => a.place.friendly_id ) %> the marked a.place is the spot, that produces these extra queries.

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  • Recovering from apt-get upgrade gone wrong due to a full disk

    - by Peter
    I was performing an apt-get upgrade on an Ubuntu 12.04.5 LTS box that hadn't been updated in a little while and the upgrade failed due to 'No space left on device'. After a little while I worked out space meant inodes and I have freed some up but unfortunately things have been left something askew. I have tried manually installing the old versions of packages mentioned using dpkg -i but that doesn't help. I have tried apt-get upgrade and apt-get -f install to no avail. Results are below. Any ideas how to fix things up? FIXED: Installing the earlier versions again manually via dpkg -i and then apt-get -f install has done the trick. Not sure why this didn't work the first time. The packages in question are listed below but they will presumably vary. libssl1.0.0_1.0.1-4ubuntu5.14_i386.deb linux-headers-3.2.0-64-generic-pae_3.2.0-64.97_i386.deb linux-image-generic-pae_3.2.0.64.76_i386.deb linux-headers-3.2.0-64_3.2.0-64.97_all.deb linux-headers-generic-pae_3.2.0.64.76_i386.deb root@unlinked:/tmp# apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done You might want to run ‘apt-get -f install’ to correct these. The following packages have unmet dependencies. libssl-dev : Depends: libssl1.0.0 (= 1.0.1-4ubuntu5.14) but 1.0.1-4ubuntu5.17 is installed linux-generic-pae : Depends: linux-image-generic-pae (= 3.2.0.64.76) but 3.2.0.67.79 is installed Depends: linux-headers-generic-pae (= 3.2.0.64.76) but 3.2.0.67.79 is installed E: Unmet dependencies. Try using -f. root@unlinked:/tmp# apt-get -f install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required: linux-headers-3.2.0-43-generic-pae linux-headers-3.2.0-38-generic-pae linux-headers-3.2.0-41-generic-pae linux-headers-3.2.0-36-generic-pae linux-headers-3.2.0-63-generic-pae linux-headers-3.2.0-58-generic-pae linux-headers-3.2.0-60-generic-pae linux-headers-3.2.0-55-generic-pae linux-headers-3.2.0-40 linux-headers-3.2.0-41 linux-headers-3.2.0-36 linux-headers-3.2.0-37 linux-headers-3.2.0-43 linux-headers-3.2.0-38 linux-headers-3.2.0-44 linux-headers-3.2.0-39 linux-headers-3.2.0-45 linux-headers-3.2.0-51 linux-headers-3.2.0-52 linux-headers-3.2.0-53 linux-headers-3.2.0-48 linux-headers-3.2.0-54 linux-headers-3.2.0-60 linux-headers-3.2.0-55 linux-headers-3.2.0-61 linux-headers-3.2.0-56 linux-headers-3.2.0-57 linux-headers-3.2.0-63 linux-headers-3.2.0-58 linux-headers-3.2.0-59 linux-headers-3.2.0-52-generic-pae linux-headers-3.2.0-44-generic-pae linux-headers-3.2.0-39-generic-pae linux-headers-3.2.0-37-generic-pae linux-headers-3.2.0-59-generic-pae linux-headers-3.2.0-61-generic-pae linux-headers-3.2.0-56-generic-pae linux-headers-3.2.0-53-generic-pae linux-headers-3.2.0-48-generic-pae linux-headers-3.2.0-45-generic-pae linux-headers-3.2.0-40-generic-pae linux-headers-3.2.0-57-generic-pae linux-headers-3.2.0-54-generic-pae linux-headers-3.2.0-51-generic-pae Use 'apt-get autoremove' to remove them. The following extra packages will be installed: libssl-dev linux-generic-pae The following packages will be upgraded: libssl-dev linux-generic-pae 2 to upgrade, 0 to newly install, 0 to remove and 0 not to upgrade. 2 not fully installed or removed. Need to get 0 B/1,427 kB of archives. After this operation, 1,024 B of additional disk space will be used. Do you want to continue [Y/n]? y dpkg: dependency problems prevent configuration of libssl-dev: libssl-dev depends on libssl1.0.0 (= 1.0.1-4ubuntu5.14); however: Version of libssl1.0.0 on system is 1.0.1-4ubuntu5.17. dpkg: error processing libssl-dev (--configure): dependency problems - leaving unconfigured No apport report written because the error message indicates it's a follow-up error from a previous failure. dpkg: dependency problems prevent configuration of linux-generic-pae: linux-generic-pae depends on linux-image-generic-pae (= 3.2.0.64.76); however: Version of linux-image-generic-pae on system is 3.2.0.67.79. linux-generic-pae depends on linux-headers-generic-pae (= 3.2.0.64.76); however: Version of linux-headers-generic-pae on system is 3.2.0.67.79. dpkg: error processing linux-generic-pae (--configure): dependency problems - leaving unconfigured No apport report written because the error message indicates it's a follow-up error from a previous failure. Errors were encountered while processing: libssl-dev linux-generic-pae E: Sub-process /usr/bin/dpkg returned an error code (1)

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  • JPA Inheritance and Relations - Clarification question

    - by Michael
    Here the scenario: I have a unidirectional 1:N Relation from Person Entity to Address Entity. And a bidirectional 1:N Relation from User Entity to Vehicle Entity. Here is the Address class: @Entity public class Address implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) privat Long int ... The Vehicles Class: @Entity public class Vehicle implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @ManyToOne private User owner; ... @PreRemove protected void preRemove() { //this.owner.removeVehicle(this); } public Vehicle(User owner) { this.owner = owner; ... The Person Class: @Entity @Inheritance(strategy = InheritanceType.JOINED) @DiscriminatorColumn(name="PERSON_TYP") public class Person implements Serializable { @Id protected String username; @OneToMany(cascade = CascadeType.ALL, orphanRemoval=true) @JoinTable(name = "USER_ADDRESS", joinColumns = @JoinColumn(name = "USERNAME"), inverseJoinColumns = @JoinColumn(name = "ADDRESS_ID")) protected List<Address> addresses; ... @PreRemove protected void prePersonRemove(){ this.addresses = null; } ... The User Class which is inherited from the Person class: @Entity @Table(name = "Users") @DiscriminatorValue("USER") public class User extends Person { @OneToMany(mappedBy = "owner", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private List<Vehicle> vehicles; ... When I try to delete a User who has an address I have to use orphanremoval=true on the corresponding relation (see above) and the preRemove function where the address List is set to null. Otherwise (no orphanremoval and adress list not set to null) a foreign key contraint fails. When i try to delete a user who has an vehicle a concurrent Acces Exception is thrown when do not uncomment the "this.owner.removeVehicle(this);" in the preRemove Function of the vehicle. The thing i do not understand is that before i used this inheritance there was only a User class which had all relations: @Entity @Table(name = "Users") public class User implements Serializable { @Id protected String username; @OneToMany(mappedBy = "owner", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private List<Vehicle> vehicles; @OneToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_ADDRESS", joinColumns = @JoinColumn(name = "USERNAME") inverseJoinColumns = @JoinColumn(name = "ADDRESS_ID")) ptivate List<Address> addresses; ... No orphanremoval, and the vehicle class has used the uncommented statement above in its preRemove function. And - I could delte a user who has an address and i could delte a user who has a vehicle. So why doesn't everything work without changes when i use inheritance? I use JPA 2.0, EclipseLink 2.0.2, MySQL 5.1.x and Netbeans 6.8

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  • How do I fix dependency problems with the kernel in apt?

    - by Jon
    When trying to install new packages, either manually or with muon, I get these errors: jon@jon-desktop:~/Apps/mendeleydesktop-1.5-dev4-linux-x86_64/bin$ sudo apt-get install kupfer [sudo] password for jon: Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: kupfer : Depends: python-keybinder but it is not going to be installed Recommends: python-wnck but it is not going to be installed linux-headers-generic : Depends: linux-headers-3.2.0-20-generic but it is not installable linux-image-generic : Depends: linux-image-3.2.0-20-generic but it is not installable E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution). jon@jon-desktop:~/Apps/mendeleydesktop-1.5-dev4-linux-x86_64/bin$ sudo apt-get -f install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following extra packages will be installed: linux-generic linux-headers-generic linux-image-generic The following packages will be upgraded: linux-generic linux-headers-generic linux-image-generic 3 upgraded, 0 newly installed, 0 to remove and 2 not upgraded. 3 not fully installed or removed. Need to get 0 B/6,658 B of archives. After this operation, 0 B of additional disk space will be used. Do you want to continue [Y/n]? dpkg: dependency problems prevent configuration of linux-image-generic: linux-image-generic depends on linux-image-3.2.0-20-generic; however: Package linux-image-3.2.0-20-generic is not installed. dpkg: error processing linux-image-generic (--configure): dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure. dpkg: dependency problems prevent configuration of linux-generic: linux-generic depends on linux-image-generic (= 3.2.0.20.22); however: Package linux-image-generic is not configured yet. dpkg: error processing linux-generic (--configure): dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure. dpkg: dependency problems prevent configuration of linux-headers-generic: linux-headers-generic depends on linux-headers-3.2.0-20-generic; however: Package linux-headers-3.2.0-20-generic is not installed. dpkg: error processing linux-headers-generic (--configure): dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure. Errors were encountered while processing: linux-image-generic linux-generic linux-headers-generic E: Sub-process /usr/bin/dpkg returned an error code (1) As indicated above, I ran sudo apt-get -f install but it still tells me there are dependency issues.

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  • Failing to upgrade to linux-image-3.0.0-26-generic

    - by Dan Lee
    When I try to upgrade linux-image-3.0.0-26-generic I get following problems: dpkg-deb (subprocess): data: internal bzip2 read error: 'DATA_ERROR' dpkg-deb: error: subprocess <decompress> returned error exit status 2 dpkg: error processing /var/cache/apt/archives/linux-image-3.0.0-26-generic_3.0.0-26.42_amd64.deb (--unpack): short read on buffer copy for backend dpkg-deb during `./lib/modules/3.0.0-26-generic/kernel/drivers/scsi/fnic/fnic.ko' No apport report written because MaxReports is reached already Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.0.0-26-generic /boot/vmlinuz-3.0.0-26-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.0.0-26-generic /boot/vmlinuz-3.0.0-26-generic Errors were encountered while processing: /var/cache/apt/archives/linux-image-3.0.0-26-generic_3.0.0-26.42_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) A package failed to install. Trying to recover: dpkg: dependency problems prevent configuration of linux-image-generic: linux-image-generic depends on linux-image-3.0.0-26-generic; however: Package linux-image-3.0.0-26-generic is not installed. I don't know why this happens to me; earlier upgrades always worked without problems. Does anybody know how to fix this?

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  • Generic socket 940 CPU fan interchangeable with HP part number 411454-001

    - by ConcernedOfTunbridgeWells
    Hi, I'm trying to find a generic CPU fan that will fit the air duct in an XW9300. Note that there are two CPU fan mounting schemes used on this machine. One with two grommets in the motherboard that the CPU fan screws into and one with a plastic collar and base plate. The form factor I'm looking for is the former (see picture below): Two HP part numbers for fans in this form factor are 411454-001 (shown below) and 416055-001. Note that the dimensions are important as the machine has an air duct that fits over the fan. Can anyone tell me the manufacturer and model of an equivalent generic part? Better yet, do you know somewhere (preferrably in the UK) that I can obtain such an item from?

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  • Generic socket 940 CPU fan for HP XW9300 interchangeable with HP part number 411454-001

    - by ConcernedOfTunbridgeWells
    Hi, I'm trying to find a generic Socket 940 CPU fan that will fit the air duct in an XW9300. Note that two different CPU fan mounting schemes have been used on this machine. One has two grommets in the motherboard that the CPU fan screws into and the other has a plastic collar and base plate. The form factor I'm looking for is the former (see the picture below). Two HP part numbers for fans in this form factor are 411454-001 (shown below) and 416055-001. Note that the dimensions are important as the machine has an air duct that fits over the fan. Can anyone tell me the manufacturer and model of an equivalent generic part? Better yet, do you know somewhere (preferrably in the UK) from which such an item can be obtained?

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  • get_or_create generic relations in Django & python debugging in general

    - by rabidpebble
    I ran the code to create the generically related objects from this demo: http://www.djangoproject.com/documentation/models/generic_relations/ Everything is good intially: >>> bacon.tags.create(tag="fatty") <TaggedItem: fatty> >>> tag, newtag = bacon.tags.get_or_create(tag="fatty") >>> tag <TaggedItem: fatty> >>> newtag False But then the use case that I'm interested in for my app: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome") Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 123, in get_or_create return self.get_query_set().get_or_create(**kwargs) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 343, in get_or_create raise e IntegrityError: app_taggeditem.content_type_id may not be NULL I tried a bunch of random things after looking at other code: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem) ValueError: Cannot assign "<class 'generics.app.models.TaggedItem'>": "TaggedItem.content_type" must be a "ContentType" instance. or: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem.content_type) InterfaceError: Error binding parameter 3 - probably unsupported type. etc. I'm sure somebody can give me the correct syntax, but the real problem here is that I have no idea what is going on. I have developed in strongly typed languages for over ten years (x86 assembly, C++ and C#) but am new to Python. I find it really difficult to follow what is going on in Python when things like this break. In the languages I mentioned previously it's fairly straightforward to figure things like this out -- check the method signature and check your parameters. Looking at the Django documentation for half an hour left me just as lost. Looking at the source for get_or_create(self, **kwargs) didn't help either since there is no method signature and the code appears very generic. A next step would be to debug the method and try to figure out what is happening, but this seems a bit extreme... I seem to be missing some fundamental operating principle here... what is it? How do I resolve issues like this on my own in the future?

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  • Ubuntu 12.04 updates fail recently - Please help

    - by user74152
    I upgraded Ubuntu 11.10 to 12.04 LTS immediately after its release (april 2012). Since then updates (new kernels and others) succeeded regularly, but recently, suddenly, updates fail consistently. What causes the problem and how can it be solved? Terminal information after the last update attempt: ariel@ariel-MS-7592:~$ sudo apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 3 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Do you want to continue [Y/n]? y Setting up linux-image-3.2.0-26-generic (3.2.0-26.41) ... Running depmod. update-initramfs: deferring update (hook will be called later) Examining /etc/kernel/postinst.d. run-parts: executing /etc/kernel/postinst.d/dkms 3.2.0-26-generic /boot/vmlinuz-3.2.0-26-generic run-parts: executing /etc/kernel/postinst.d/initramfs-tools 3.2.0-26-generic /boot/vmlinuz-3.2.0-26-generic update-initramfs: Generating /boot/initrd.img-3.2.0-26-generic run-parts: executing /etc/kernel/postinst.d/pm-utils 3.2.0-26-generic /boot/vmlinuz-3.2.0-26-generic run-parts: executing /etc/kernel/postinst.d/update-notifier 3.2.0-26-generic /boot/vmlinuz-3.2.0-26-generic run-parts: executing /etc/kernel/postinst.d/zz-update-grub 3.2.0-26-generic /boot/vmlinuz-3.2.0-26-generic /usr/sbin/grub-mkconfig: 11: /etc/default/grub: splash”: not found run-parts: /etc/kernel/postinst.d/zz-update-grub exited with return code 127 Failed to process /etc/kernel/postinst.d at /var/lib/dpkg/info/linux-image-3.2.0-26-generic.postinst line 1010. dpkg: error processing linux-image-3.2.0-26-generic (--configure): subprocess installed post-installation script returned error exit status 2 No apport report written because MaxReports is reached already dpkg: dependency problems prevent configuration of linux-image-generic: linux-image-generic depends on linux-image-3.2.0-26-generic; however: Package linux-image-3.2.0-26-generic is not configured yet. dpkg: error processing linux-image-generic (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of linux-generic: linux-generic depends on linux-image-generic (= 3.2.0.26.28); however: Package linux-image-generic is not configured yet. dpkg: error processing linux-generic (--configure): dependency problems - leaving unconfiguredNo apport report written because MaxReports is reached already No apport report written because MaxReports is reached already Errors were encountered while processing: linux-image-3.2.0-26-generic linux-image-generic linux-generic E: Sub-process /usr/bin/dpkg returned an error code (1)

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  • Implement a generic C++/CLI interface in a C# generic interface

    - by Florent
    I have a C++/CLI generic interface like this : using namespace System::Collections::Generic; namespace Test { generic <class T> public interface class IElementList { property List<T>^ Elements; }; } and I want to implement it in a C# generic interface like this : using Test; namespace U { public interface IElementLightList<T> : IElementList<T> where T : IElementLight { bool isFrozen(); bool isPastable(); } } This don't work, Visual Studio is not able to see C++/CLI IElementList interface ! I tested with a not generic C++/CLI interface and this work. What I missed ?

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  • In plain English, what are Django generic views?

    - by allyourcode
    The first two paragraphs of this page explain that generic views are supposed to make my life easier, less monotonous, and make me more attractive to women (I made up that last one): http://docs.djangoproject.com/en/dev/topics/generic-views/#topics-generic-views I'm all for improving my life, but what do generic views actually do? It seems like lots of buzzwords are being thrown around, which confuse more than they explain. Are generic views similar to scaffolding in Ruby on Rails? The last bullet point in the intro seems to indicate this. Is that an accurate statement?

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  • Dynamically creating a Generic Type at Runtime

    - by Rick Strahl
    I learned something new today. Not uncommon, but it's a core .NET runtime feature I simply did not know although I know I've run into this issue a few times and worked around it in other ways. Today there was no working around it and a few folks on Twitter pointed me in the right direction. The question I ran into is: How do I create a type instance of a generic type when I have dynamically acquired the type at runtime? Yup it's not something that you do everyday, but when you're writing code that parses objects dynamically at runtime it comes up from time to time. In my case it's in the bowels of a custom JSON parser. After some thought triggered by a comment today I realized it would be fairly easy to implement two-way Dictionary parsing for most concrete dictionary types. I could use a custom Dictionary serialization format that serializes as an array of key/value objects. Basically I can use a custom type (that matches the JSON signature) to hold my parsed dictionary data and then add it to the actual dictionary when parsing is complete. Generic Types at Runtime One issue that came up in the process was how to figure out what type the Dictionary<K,V> generic parameters take. Reflection actually makes it fairly easy to figure out generic types at runtime with code like this: if (arrayType.GetInterface("IDictionary") != null) { if (arrayType.IsGenericType) { var keyType = arrayType.GetGenericArguments()[0]; var valueType = arrayType.GetGenericArguments()[1]; … } } The GetArrayType method gets passed a type instance that is the array or array-like object that is rendered in JSON as an array (which includes IList, IDictionary, IDataReader and a few others). In my case the type passed would be something like Dictionary<string, CustomerEntity>. So I know what the parent container class type is. Based on the the container type using it's then possible to use GetGenericTypeArguments() to retrieve all the generic types in sequential order of definition (ie. string, CustomerEntity). That's the easy part. Creating a Generic Type and Providing Generic Parameters at RunTime The next problem is how do I get a concrete type instance for the generic type? I know what the type name and I have a type instance is but it's generic, so how do I get a type reference to keyvaluepair<K,V> that is specific to the keyType and valueType above? Here are a couple of things that come to mind but that don't work (and yes I tried that unsuccessfully first): Type elementType = typeof(keyvalue<keyType, valueType>); Type elementType = typeof(keyvalue<typeof(keyType), typeof(valueType)>); The problem is that this explicit syntax expects a type literal not some dynamic runtime value, so both of the above won't even compile. I turns out the way to create a generic type at runtime is using a fancy bit of syntax that until today I was completely unaware of: Type elementType = typeof(keyvalue<,>).MakeGenericType(keyType, valueType); The key is the type(keyvalue<,>) bit which looks weird at best. It works however and produces a non-generic type reference. You can see the difference between the full generic type and the non-typed (?) generic type in the debugger: The nonGenericType doesn't show any type specialization, while the elementType type shows the string, CustomerEntity (truncated above) in the type name. Once the full type reference exists (elementType) it's then easy to create an instance. In my case the parser parses through the JSON and when it completes parsing the value/object it creates a new keyvalue<T,V> instance. Now that I know the element type that's pretty trivial with: // Objects start out null until we find the opening tag resultObject = Activator.CreateInstance(elementType); Here the result object is picked up by the JSON array parser which creates an instance of the child object (keyvalue<K,V>) and then parses and assigns values from the JSON document using the types  key/value property signature. Internally the parser then takes each individually parsed item and adds it to a list of  List<keyvalue<K,V>> items. Parsing through a Generic type when you only have Runtime Type Information When parsing of the JSON array is done, the List needs to be turned into a defacto Dictionary<K,V>. This should be easy since I know that I'm dealing with an IDictionary, and I know the generic types for the key and value. The problem is again though that this needs to happen at runtime which would mean using several Convert.ChangeType() calls in the code to dynamically cast at runtime. Yuk. In the end I decided the easier and probably only slightly slower way to do this is a to use the dynamic type to collect the items and assign them to avoid all the dynamic casting madness: else if (IsIDictionary) { IDictionary dict = Activator.CreateInstance(arrayType) as IDictionary; foreach (dynamic item in items) { dict.Add(item.key, item.value); } return dict; } This code creates an instance of the generic dictionary type first, then loops through all of my custom keyvalue<K,V> items and assigns them to the actual dictionary. By using Dynamic here I can side step all the explicit type conversions that would be required in the three highlighted areas (not to mention that this nested method doesn't have access to the dictionary item generic types here). Static <- -> Dynamic Dynamic casting in a static language like C# is a bitch to say the least. This is one of the few times when I've cursed static typing and the arcane syntax that's required to coax types into the right format. It works but it's pretty nasty code. If it weren't for dynamic that last bit of code would have been a pretty ugly as well with a bunch of Convert.ChangeType() calls to litter the code. Fortunately this type of type convulsion is rather rare and reserved for system level code. It's not every day that you create a string to object parser after all :-)© Rick Strahl, West Wind Technologies, 2005-2011Posted in .NET  CSharp   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • some files just wont install- linux-image-3.5.0-42-generic

    - by jatin
    It gives the following details of the package operation failing after using the sofware updater on 12.10: installArchives() failed: perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LANGUAGE = (unset), LC_ALL = (unset), LANG = "en_IN.ISO8859-1" are supported and installed on your system. perl: warning: Falling back to the standard locale ("C"). locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory Preconfiguring packages ... perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LANGUAGE = (unset), LC_ALL = (unset), LANG = "en_IN.ISO8859-1" are supported and installed on your system. perl: warning: Falling back to the standard locale ("C"). locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory Preconfiguring packages ... perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LANGUAGE = (unset), LC_ALL = (unset), LANG = "en_IN.ISO8859-1" are supported and installed on your system. perl: warning: Falling back to the standard locale ("C"). locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory Preconfiguring packages ... perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LANGUAGE = (unset), LC_ALL = (unset), LANG = "en_IN.ISO8859-1" are supported and installed on your system. perl: warning: Falling back to the standard locale ("C"). locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory Preconfiguring packages ... (Reading database ... (Reading database ... 217566 files and directories currently installed.) Preparing to replace linux-image-3.5.0-36-generic 3.5.0-36.57~precise1 (using .../linux-image-3.5.0-36-generic_3.5.0-36.57_amd64.deb) ... locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory Done. Unpacking replacement linux-image-3.5.0-36-generic ... dpkg: error processing /var/cache/apt/archives/linux-image-3.5.0-36-generic_3.5.0-36.57_amd64.deb (--unpack): unable to make backup link of `./boot/System.map-3.5.0-36-generic' before installing new version: Operation not permitted No apport report written because MaxReports is reached already dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.5.0-36-generic /boot/vmlinuz-3.5.0-36-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.5.0-36-generic /boot/vmlinuz-3.5.0-36-generic Preparing to replace linux-image-3.5.0-42-generic 3.5.0-42.65~precise1 (using .../linux-image-3.5.0-42-generic_3.5.0-42.65_amd64.deb) ... locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory Done. Unpacking replacement linux-image-3.5.0-42-generic ... dpkg: error processing /var/cache/apt/archives/linux-image-3.5.0-42-generic_3.5.0-42.65_amd64.deb (--unpack): unable to make backup link of `./boot/System.map-3.5.0-42-generic' before installing new version: Operation not permitted No apport report written because MaxReports is reached already Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.5.0-42-generic /boot/vmlinuz-3.5.0-42-generic dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.5.0-42-generic /boot/vmlinuz-3.5.0-42-generic Preparing to replace memtest86+ 4.20-1.1ubuntu1 (using .../memtest86+_4.20-1.1ubuntu2.1_amd64.deb) ... Unpacking replacement memtest86+ ... dpkg: error processing /var/cache/apt/archives/memtest86+_4.20-1.1ubuntu2.1_amd64.deb (--unpack): unable to make backup link of `./boot/memtest86+.bin' before installing new version: Operation not permitted No apport report written because MaxReports is reached already locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_MESSAGES to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory Errors were encountered while processing: /var/cache/apt/archives/linux-image-3.5.0-36-generic_3.5.0-36.57_amd64.deb /var/cache/apt/archives/linux-image-3.5.0-42-generic_3.5.0-42.65_amd64.deb /var/cache/apt/archives/memtest86+_4.20-1.1ubuntu2.1_amd64.deb Error in function: Output of df -h: Filesystem Size Used Avail Use% Mounted on /dev/sda6 38G 6.5G 30G 19% / udev 3.5G 4.0K 3.5G 1% /dev tmpfs 1.5G 924K 1.5G 1% /run none 5.0M 4.0K 5.0M 1% /run/lock none 3.6G 296K 3.6G 1% /run/shm none 100M 64K 100M 1% /run/user /dev/sda1 197M 87M 111M 44% /boot /dev/sda5 243G 971M 230G 1% /home

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  • WCF: Serializing and Deserializing generic collections

    - by Fabiano
    I have a class Team that holds a generic list: [DataContract(Name = "TeamDTO", IsReference = true)] public class Team { [DataMember] private IList<Person> members = new List<Person>(); public Team() { Init(); } private void Init() { members = new List<Person>(); } [System.Runtime.Serialization.OnDeserializing] protected void OnDeserializing(StreamingContext ctx) { Log("OnDeserializing of Team called"); Init(); if (members != null) Log(members.ToString()); } [System.Runtime.Serialization.OnSerializing] private void OnSerializing(StreamingContext ctx) { Log("OnSerializing of Team called"); if (members != null) Log(members.ToString()); } [System.Runtime.Serialization.OnDeserialized] protected void OnDeserialized(StreamingContext ctx) { Log("OnDeserialized of Team called"); if (members != null) Log(members.ToString()); } [System.Runtime.Serialization.OnSerialized] private void OnSerialized(StreamingContext ctx) { Log("OnSerialized of Team called"); Log(members.ToString()); } When I use this class in a WCF service, I get following log output OnSerializing of Team called System.Collections.Generic.List 1[Person] OnSerialized of Team called System.Collections.Generic.List 1[Person] OnDeserializing of Team called System.Collections.Generic.List 1[ENetLogic.ENetPerson.Model.FirstPartyPerson] OnDeserialized of Team called ENetLogic.ENetPerson.Model.Person[] After the deserialization members is an Array and no longer a generic list although the field type is IList< (?!) When I try to send this object back over the WCF service I get the log output OnSerializing of Team called ENetLogic.ENetPerson.Model.FirstPartyPerson[] After this my unit test crashes with a System.ExecutionEngineException, which means the WCF service is not able to serialize the array. (maybe because it expected a IList<) So, my question is: Does anybody know why the type of my IList< is an array after deserializing and why I can't serialize my Team object any longer after that? Thanks

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  • How to check if a generic type definition inherits from another generic type definition

    - by Anne
    I'm trying to check whether an open generic type definition implements some open generic interface. Look at the sample below: public interface IService<T> { } public class ServiceImpl<T> : IService<T> { } private static bool OpenGenericTypeImplementsOpenGenericInterface( Type derivedType, Type interfaceType) { return derivedType.GetInterfaces().Contains(interfaceType); } [TestMethod] public void Verify() { Type openGenericImplementation = typeof(ServiceImpl<>); Type expectedInterfaceType = typeof(IService<>); bool implDoesImplementInterface = OpenGenericTypeImplementsOpenGenericInterface( openGenericImplementation, expectedInterfaceType); // This assert fails. Why? Assert.IsTrue(implDoesImplementInterface); } I found out that the returned type from the Type.GetInterfaces() method does not match the type returned from typeof(IService<>). I can't figure out why that is and how to correctly validate whether some generic type definition inherits or implements some other generic type definition. What's going on here and how do I solve fix this problem?

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  • 'Generic' ViewModel

    - by Ian MacPherson
    Using EF 4, I have several subtypes of a 'Business' entity (customers, suppliers, haulage companies etc). They DO need to be subtypes. I am building a general viewmodel which calls into a service from which a generic repository is accessed. As I have 4 subtypes, it would be good to have a 'generic' viewmodel used for all of these. Problem is of course is that I have to call a specific type into my generic repository, for example: BusinessToRetrieve = _repository .LoadEntity<Customer>(o => o.CustomerID == customerID); It would be good to be able to call <SomethingElse>, somethingElse being one or other of the subtypes), otherwise I shall have to create 4 near identical viemodels, which seems a waste of course! The subtype entity name is available to the viewmodel but I've been unable to figure out how to make the above call convert this into a type. An issue with achieving what I want is that presumably the lambda expression being passed in wouldn't be able to resolve on a 'generic' call ?

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  • Django generic relation field reports that all() is getting unexpected keyword argument when no args

    - by Joshua
    I have a model which can be attached to to other models. class Attachable(models.Model): content_type = models.ForeignKey(ContentType) object_pk = models.TextField() content_object = generic.GenericForeignKey(ct_field="content_type", fk_field="object_pk") class Meta: abstract = True class Flag(Attachable): user = models.ForeignKey(User) flag = models.SlugField() timestamp = models.DateTimeField() I'm creating a generic relationship to this model in another model. flags = generic.GenericRelation(Flag) I try to get objects from this generic relation like so: self.flags.all() This results in the following exception: >>> obj.flags.all() Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 105, in all return self.get_query_set() File "/usr/local/lib/python2.6/dist-packages/django/contrib/contenttypes/generic.py", line 252, in get_query_set return superclass.get_query_set(self).filter(**query) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 498, in filter return self._filter_or_exclude(False, *args, **kwargs) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 516, in _filter_or_exclude clone.query.add_q(Q(*args, **kwargs)) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1675, in add_q can_reuse=used_aliases) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1569, in add_filter negate=negate, process_extras=process_extras) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1737, in setup_joins "Choices are: %s" % (name, ", ".join(names))) FieldError: Cannot resolve keyword 'object_id' into field. Choices are: content_type, flag, id, nestablecomment, object_pk, timestamp, user >>> obj.flags.all(object_pk=obj.pk) Traceback (most recent call last): File "<console>", line 1, in <module> TypeError: all() got an unexpected keyword argument 'object_pk' What have I done wrong?

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  • When/Why ( if ever ) should i think about doing Generic Programming/Meta Programming

    - by hotadvice
    Hi there IMHO to me OOPS, design patterns make sense and i have been able to apply them practically. But when it comes to "generic programming /meta programming" of the Modern C++ kind, i am left confused. -- Is it a new programming/design paradigm ? -- Is it just limited to "library development"? If not, What design/coding situations call for using meta programming/generic programming. -- Does using templates mean i am doing generic programming? I have googled a lot on this topic but do not grasp the BIG PICTURE fully. Also see this post. After reading dicussions here under, up till now, I am sure ( might still not be correct): a) Generic programming and meta programming are two different concepts.

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  • How to get rid of grub menu after boot?

    - by umpirsky
    Here is my /etc/default/grub: # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. GRUB_DEFAULT=0 GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" GRUB_CMDLINE_LINUX="" # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' #GRUB_GFXMODE=640x480 # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID=true # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_LINUX_RECOVERY="true" # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1" I tried various things including: How do I hide the GRUB menu showing up in the beginning of boot? How to disable Grub's menu from showing up after failed boot http://www.itworld.com/software/306238/disable-grub-boot-menu-ubuntu-1210 But I still get grub menu each time I boot. My generated /boot/grub/grub.cfg: # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi if [ "${next_entry}" ] ; then set default="${next_entry}" set next_entry= save_env next_entry set boot_once=true else set default="0" fi if [ x"${feature_menuentry_id}" = xy ]; then menuentry_id_option="--id" else menuentry_id_option="" fi export menuentry_id_option if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { if [ x$feature_all_video_module = xy ]; then insmod all_video else insmod efi_gop insmod efi_uga insmod ieee1275_fb insmod vbe insmod vga insmod video_bochs insmod video_cirrus fi } if [ x$feature_default_font_path = xy ] ; then font=unicode else insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi font="/usr/share/grub/unicode.pf2" fi if loadfont $font ; then set gfxmode=auto load_video insmod gfxterm set locale_dir=$prefix/locale set lang=en_US insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ] ; then set timeout=-1 else if [ x$feature_timeout_style = xy ] ; then set timeout_style=hidden set timeout=0 # Fallback hidden-timeout code in case the timeout_style feature is # unavailable. elif sleep --interruptible 0 ; then set timeout=0 fi fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 45,51,53; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### function gfxmode { set gfxpayload="${1}" if [ "${1}" = "keep" ]; then set vt_handoff=vt.handoff=7 else set vt_handoff= fi } if [ "${recordfail}" != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-ed6b32bc-ec1d-444c-a000-282fddd6d460' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi linux /boot/vmlinuz-3.13.0-29-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro quiet splash $vt_handoff initrd /boot/initrd.img-3.13.0-29-generic } submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-ed6b32bc-ec1d-444c-a000-282fddd6d460' { menuentry 'Ubuntu, with Linux 3.13.0-29-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-29-generic-advanced-ed6b32bc-ec1d-444c-a000-282fddd6d460' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi echo 'Loading Linux 3.13.0-29-generic ...' linux /boot/vmlinuz-3.13.0-29-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro quiet splash $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-29-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-29-generic-recovery-ed6b32bc-ec1d-444c-a000-282fddd6d460' { recordfail load_video insmod gzio insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi echo 'Loading Linux 3.13.0-29-generic ...' linux /boot/vmlinuz-3.13.0-29-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-24-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-24-generic-advanced-ed6b32bc-ec1d-444c-a000-282fddd6d460' { recordfail load_video gfxmode $linux_gfx_mode insmod gzio insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi echo 'Loading Linux 3.13.0-24-generic ...' linux /boot/vmlinuz-3.13.0-24-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro quiet splash $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-24-generic } menuentry 'Ubuntu, with Linux 3.13.0-24-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.13.0-24-generic-recovery-ed6b32bc-ec1d-444c-a000-282fddd6d460' { recordfail load_video insmod gzio insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi echo 'Loading Linux 3.13.0-24-generic ...' linux /boot/vmlinuz-3.13.0-24-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.13.0-24-generic } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### menuentry 'Ubuntu 14.04 LTS (14.04) (on /dev/mapper/isw_beaaegcdjh_ASUS_OS2)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-simple-ed6b32bc-ec1d-444c-a000-282fddd6d460' { insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi linux /boot/vmlinuz-3.13.0-29-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro splash quiet quiet splash $vt_handoff initrd /boot/initrd.img-3.13.0-29-generic } submenu 'Advanced options for Ubuntu 14.04 LTS (14.04) (on /dev/mapper/isw_beaaegcdjh_ASUS_OS2)' $menuentry_id_option 'osprober-gnulinux-advanced-ed6b32bc-ec1d-444c-a000-282fddd6d460' { menuentry 'Ubuntu (on /dev/mapper/isw_beaaegcdjh_ASUS_OS2)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-3.13.0-29-generic.efi.signed--ed6b32bc-ec1d-444c-a000-282fddd6d460' { insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi linux /boot/vmlinuz-3.13.0-29-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro splash quiet quiet splash $vt_handoff initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-29-generic (on /dev/mapper/isw_beaaegcdjh_ASUS_OS2)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-3.13.0-29-generic.efi.signed--ed6b32bc-ec1d-444c-a000-282fddd6d460' { insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi linux /boot/vmlinuz-3.13.0-29-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro splash quiet quiet splash $vt_handoff initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-29-generic (recovery mode) (on /dev/mapper/isw_beaaegcdjh_ASUS_OS2)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-3.13.0-29-generic.efi.signed-root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro recovery nomodeset splash quiet-ed6b32bc-ec1d-444c-a000-282fddd6d460' { insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi linux /boot/vmlinuz-3.13.0-29-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro recovery nomodeset splash quiet initrd /boot/initrd.img-3.13.0-29-generic } menuentry 'Ubuntu, with Linux 3.13.0-24-generic (on /dev/mapper/isw_beaaegcdjh_ASUS_OS2)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-3.13.0-24-generic.efi.signed--ed6b32bc-ec1d-444c-a000-282fddd6d460' { insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi linux /boot/vmlinuz-3.13.0-24-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro splash quiet quiet splash $vt_handoff initrd /boot/initrd.img-3.13.0-24-generic } menuentry 'Ubuntu, with Linux 3.13.0-24-generic (recovery mode) (on /dev/mapper/isw_beaaegcdjh_ASUS_OS2)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-3.13.0-24-generic.efi.signed-root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro recovery nomodeset splash quiet-ed6b32bc-ec1d-444c-a000-282fddd6d460' { insmod part_gpt insmod ext2 if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 else search --no-floppy --fs-uuid --set=root ed6b32bc-ec1d-444c-a000-282fddd6d460 fi linux /boot/vmlinuz-3.13.0-24-generic.efi.signed root=UUID=ed6b32bc-ec1d-444c-a000-282fddd6d460 ro recovery nomodeset splash quiet initrd /boot/initrd.img-3.13.0-24-generic } } set timeout_style=menu if [ "${timeout}" = 0 ]; then set timeout=10 fi ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/30_uefi-firmware ### menuentry 'System setup' $menuentry_id_option 'uefi-firmware' { fwsetup } ### END /etc/grub.d/30_uefi-firmware ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f ${config_directory}/custom.cfg ]; then source ${config_directory}/custom.cfg elif [ -z "${config_directory}" -a -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ###

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  • Dynamic Code for type casting Generic Types 'generically' in C#

    - by Rick Strahl
    C# is a strongly typed language and while that's a fundamental feature of the language there are more and more situations where dynamic types make a lot of sense. I've written quite a bit about how I use dynamic for creating new type extensions: Dynamic Types and DynamicObject References in C# Creating a dynamic, extensible C# Expando Object Creating a dynamic DataReader for dynamic Property Access Today I want to point out an example of a much simpler usage for dynamic that I use occasionally to get around potential static typing issues in C# code especially those concerning generic types. TypeCasting Generics Generic types have been around since .NET 2.0 I've run into a number of situations in the past - especially with generic types that don't implement specific interfaces that can be cast to - where I've been unable to properly cast an object when it's passed to a method or assigned to a property. Granted often this can be a sign of bad design, but in at least some situations the code that needs to be integrated is not under my control so I have to make due with what's available or the parent object is too complex or intermingled to be easily refactored to a new usage scenario. Here's an example that I ran into in my own RazorHosting library - so I have really no excuse, but I also don't see another clean way around it in this case. A Generic Example Imagine I've implemented a generic type like this: public class RazorEngine<TBaseTemplateType> where TBaseTemplateType : RazorTemplateBase, new() You can now happily instantiate new generic versions of this type with custom template bases or even a non-generic version which is implemented like this: public class RazorEngine : RazorEngine<RazorTemplateBase> { public RazorEngine() : base() { } } To instantiate one: var engine = new RazorEngine<MyCustomRazorTemplate>(); Now imagine that the template class receives a reference to the engine when it's instantiated. This code is fired as part of the Engine pipeline when it gets ready to execute the template. It instantiates the template and assigns itself to the template: var template = new TBaseTemplateType() { Engine = this } The problem here is that possibly many variations of RazorEngine<T> can be passed. I can have RazorTemplateBase, RazorFolderHostTemplateBase, CustomRazorTemplateBase etc. as generic parameters and the Engine property has to reflect that somehow. So, how would I cast that? My first inclination was to use an interface on the engine class and then cast to the interface.  Generally that works, but unfortunately here the engine class is generic and has a few members that require the template type in the member signatures. So while I certainly can implement an interface: public interface IRazorEngine<TBaseTemplateType> it doesn't really help for passing this generically templated object to the template class - I still can't cast it if multiple differently typed versions of the generic type could be passed. I have the exact same issue in that I can't specify a 'generic' generic parameter, since there's no underlying base type that's common. In light of this I decided on using object and the following syntax for the property (and the same would be true for a method parameter): public class RazorTemplateBase :MarshalByRefObject,IDisposable { public object Engine {get;set; } } Now because the Engine property is a non-typed object, when I need to do something with this value, I still have no way to cast it explicitly. What I really would need is: public RazorEngine<> Engine { get; set; } but that's not possible. Dynamic to the Rescue Luckily with the dynamic type this sort of thing can be mitigated fairly easily. For example here's a method that uses the Engine property and uses the well known class interface by simply casting the plain object reference to dynamic and then firing away on the properties and methods of the base template class that are common to all templates:/// <summary> /// Allows rendering a dynamic template from a string template /// passing in a model. This is like rendering a partial /// but providing the input as a /// </summary> public virtual string RenderTemplate(string template,object model) { if (template == null) return string.Empty; // if there's no template markup if(!template.Contains("@")) return template; // use dynamic to get around generic type casting dynamic engine = Engine; string result = engine.RenderTemplate(template, model); if (result == null) throw new ApplicationException("RenderTemplate failed: " + engine.ErrorMessage); return result; } Prior to .NET 4.0  I would have had to use Reflection for this sort of thing which would have a been a heck of a lot more verbose, but dynamic makes this so much easier and cleaner and in this case at least the overhead is negliable since it's a single dynamic operation on an otherwise very complex operation call. Dynamic as  a Bailout Sometimes this sort of thing often reeks of a design flaw, and I agree that in hindsight this could have been designed differently. But as is often the case this particular scenario wasn't planned for originally and removing the generic signatures from the base type would break a ton of other code in the framework. Given the existing fairly complex engine design, refactoring an interface to remove generic types just to make this particular code work would have been overkill. Instead dynamic provides a nice and simple and relatively clean solution. Now if there were many other places where this occurs I would probably consider reworking the code to make this cleaner but given this isolated instance and relatively low profile operation use of dynamic seems a valid choice for me. This solution really works anywhere where you might end up with an inheritance structure that doesn't have a common base or interface that is sufficient. In the example above I know what I'm getting but there's no common base type that I can cast to. All that said, it's a good idea to think about use of dynamic before you rush in. In many situations there are alternatives that can still work with static typing. Dynamic definitely has some overhead compared to direct static access of objects, so if possible we should definitely stick to static typing. In the example above the application already uses dynamics extensively for dynamic page page templating and passing models around so introducing dynamics here has very little additional overhead. The operation itself also fires of a fairly resource heavy operation where the overhead of a couple of dynamic member accesses are not a performance issue. So, what's your experience with dynamic as a bailout mechanism? © Rick Strahl, West Wind Technologies, 2005-2012Posted in CSharp   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • C#/.NET Little Wonders: The Generic Func Delegates

    - 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. Back in one of my three original “Little Wonders” Trilogy of posts, I had listed generic delegates as one of the Little Wonders of .NET.  Later, someone posted a comment saying said that they would love more detail on the generic delegates and their uses, since my original entry just scratched the surface of them. Last week, I began our look at some of the handy generic delegates built into .NET with a description of delegates in general, and the Action family of delegates.  For this week, I’ll launch into a look at the Func family of generic delegates and how they can be used to support generic, reusable algorithms and classes. Quick Delegate Recap Delegates are similar to function pointers in C++ in that they allow you to store a reference to a method.  They can store references to either static or instance methods, and can actually be used to chain several methods together in one delegate. Delegates are very type-safe and can be satisfied with any standard method, anonymous method, or a lambda expression.  They can also be null as well (refers to no method), so care should be taken to make sure that the delegate is not null before you invoke it. Delegates are defined using the keyword delegate, where the delegate’s type name is placed where you would typically place the method name: 1: // This delegate matches any method that takes string, returns nothing 2: public delegate void Log(string message); This delegate defines a delegate type named Log that can be used to store references to any method(s) that satisfies its signature (whether instance, static, lambda expression, etc.). Delegate instances then can be assigned zero (null) or more methods using the operator = which replaces the existing delegate chain, or by using the operator += which adds a method to the end of a delegate chain: 1: // creates a delegate instance named currentLogger defaulted to Console.WriteLine (static method) 2: Log currentLogger = Console.Out.WriteLine; 3:  4: // invokes the delegate, which writes to the console out 5: currentLogger("Hi Standard Out!"); 6:  7: // append a delegate to Console.Error.WriteLine to go to std error 8: currentLogger += Console.Error.WriteLine; 9:  10: // invokes the delegate chain and writes message to std out and std err 11: currentLogger("Hi Standard Out and Error!"); While delegates give us a lot of power, it can be cumbersome to re-create fairly standard delegate definitions repeatedly, for this purpose the generic delegates were introduced in various stages in .NET.  These support various method types with particular signatures. Note: a caveat with generic delegates is that while they can support multiple parameters, they do not match methods that contains ref or out parameters. If you want to a delegate to represent methods that takes ref or out parameters, you will need to create a custom delegate. We’ve got the Func… delegates Just like it’s cousin, the Action delegate family, the Func delegate family gives us a lot of power to use generic delegates to make classes and algorithms more generic.  Using them keeps us from having to define a new delegate type when need to make a class or algorithm generic. Remember that the point of the Action delegate family was to be able to perform an “action” on an item, with no return results.  Thus Action delegates can be used to represent most methods that take 0 to 16 arguments but return void.  You can assign a method The Func delegate family was introduced in .NET 3.5 with the advent of LINQ, and gives us the power to define a function that can be called on 0 to 16 arguments and returns a result.  Thus, the main difference between Action and Func, from a delegate perspective, is that Actions return nothing, but Funcs return a result. The Func family of delegates have signatures as follows: Func<TResult> – matches a method that takes no arguments, and returns value of type TResult. Func<T, TResult> – matches a method that takes an argument of type T, and returns value of type TResult. Func<T1, T2, TResult> – matches a method that takes arguments of type T1 and T2, and returns value of type TResult. Func<T1, T2, …, TResult> – and so on up to 16 arguments, and returns value of type TResult. These are handy because they quickly allow you to be able to specify that a method or class you design will perform a function to produce a result as long as the method you specify meets the signature. For example, let’s say you were designing a generic aggregator, and you wanted to allow the user to define how the values will be aggregated into the result (i.e. Sum, Min, Max, etc…).  To do this, we would ask the user of our class to pass in a method that would take the current total, the next value, and produce a new total.  A class like this could look like: 1: public sealed class Aggregator<TValue, TResult> 2: { 3: // holds method that takes previous result, combines with next value, creates new result 4: private Func<TResult, TValue, TResult> _aggregationMethod; 5:  6: // gets or sets the current result of aggregation 7: public TResult Result { get; private set; } 8:  9: // construct the aggregator given the method to use to aggregate values 10: public Aggregator(Func<TResult, TValue, TResult> aggregationMethod = null) 11: { 12: if (aggregationMethod == null) throw new ArgumentNullException("aggregationMethod"); 13:  14: _aggregationMethod = aggregationMethod; 15: } 16:  17: // method to add next value 18: public void Aggregate(TValue nextValue) 19: { 20: // performs the aggregation method function on the current result and next and sets to current result 21: Result = _aggregationMethod(Result, nextValue); 22: } 23: } Of course, LINQ already has an Aggregate extension method, but that works on a sequence of IEnumerable<T>, whereas this is designed to work more with aggregating single results over time (such as keeping track of a max response time for a service). We could then use this generic aggregator to find the sum of a series of values over time, or the max of a series of values over time (among other things): 1: // creates an aggregator that adds the next to the total to sum the values 2: var sumAggregator = new Aggregator<int, int>((total, next) => total + next); 3:  4: // creates an aggregator (using static method) that returns the max of previous result and next 5: var maxAggregator = new Aggregator<int, int>(Math.Max); So, if we were timing the response time of a web method every time it was called, we could pass that response time to both of these aggregators to get an idea of the total time spent in that web method, and the max time spent in any one call to the web method: 1: // total will be 13 and max 13 2: int responseTime = 13; 3: sumAggregator.Aggregate(responseTime); 4: maxAggregator.Aggregate(responseTime); 5:  6: // total will be 20 and max still 13 7: responseTime = 7; 8: sumAggregator.Aggregate(responseTime); 9: maxAggregator.Aggregate(responseTime); 10:  11: // total will be 40 and max now 20 12: responseTime = 20; 13: sumAggregator.Aggregate(responseTime); 14: maxAggregator.Aggregate(responseTime); The Func delegate family is useful for making generic algorithms and classes, and in particular allows the caller of the method or user of the class to specify a function to be performed in order to generate a result. What is the result of a Func delegate chain? If you remember, we said earlier that you can assign multiple methods to a delegate by using the += operator to chain them.  So how does this affect delegates such as Func that return a value, when applied to something like the code below? 1: Func<int, int, int> combo = null; 2:  3: // What if we wanted to aggregate the sum and max together? 4: combo += (total, next) => total + next; 5: combo += Math.Max; 6:  7: // what is the result? 8: var comboAggregator = new Aggregator<int, int>(combo); Well, in .NET if you chain multiple methods in a delegate, they will all get invoked, but the result of the delegate is the result of the last method invoked in the chain.  Thus, this aggregator would always result in the Math.Max() result.  The other chained method (the sum) gets executed first, but it’s result is thrown away: 1: // result is 13 2: int responseTime = 13; 3: comboAggregator.Aggregate(responseTime); 4:  5: // result is still 13 6: responseTime = 7; 7: comboAggregator.Aggregate(responseTime); 8:  9: // result is now 20 10: responseTime = 20; 11: comboAggregator.Aggregate(responseTime); So remember, you can chain multiple Func (or other delegates that return values) together, but if you do so you will only get the last executed result. Func delegates and co-variance/contra-variance in .NET 4.0 Just like the Action delegate, as of .NET 4.0, the Func delegate family is contra-variant on its arguments.  In addition, it is co-variant on its return type.  To support this, in .NET 4.0 the signatures of the Func delegates changed to: Func<out TResult> – matches a method that takes no arguments, and returns value of type TResult (or a more derived type). Func<in T, out TResult> – matches a method that takes an argument of type T (or a less derived type), and returns value of type TResult(or a more derived type). Func<in T1, in T2, out TResult> – matches a method that takes arguments of type T1 and T2 (or less derived types), and returns value of type TResult (or a more derived type). Func<in T1, in T2, …, out TResult> – and so on up to 16 arguments, and returns value of type TResult (or a more derived type). Notice the addition of the in and out keywords before each of the generic type placeholders.  As we saw last week, the in keyword is used to specify that a generic type can be contra-variant -- it can match the given type or a type that is less derived.  However, the out keyword, is used to specify that a generic type can be co-variant -- it can match the given type or a type that is more derived. On contra-variance, if you are saying you need an function that will accept a string, you can just as easily give it an function that accepts an object.  In other words, if you say “give me an function that will process dogs”, I could pass you a method that will process any animal, because all dogs are animals.  On the co-variance side, if you are saying you need a function that returns an object, you can just as easily pass it a function that returns a string because any string returned from the given method can be accepted by a delegate expecting an object result, since string is more derived.  Once again, in other words, if you say “give me a method that creates an animal”, I can pass you a method that will create a dog, because all dogs are animals. It really all makes sense, you can pass a more specific thing to a less specific parameter, and you can return a more specific thing as a less specific result.  In other words, pay attention to the direction the item travels (parameters go in, results come out).  Keeping that in mind, you can always pass more specific things in and return more specific things out. For example, in the code below, we have a method that takes a Func<object> to generate an object, but we can pass it a Func<string> because the return type of object can obviously accept a return value of string as well: 1: // since Func<object> is co-variant, this will access Func<string>, etc... 2: public static string Sequence(int count, Func<object> generator) 3: { 4: var builder = new StringBuilder(); 5:  6: for (int i=0; i<count; i++) 7: { 8: object value = generator(); 9: builder.Append(value); 10: } 11:  12: return builder.ToString(); 13: } Even though the method above takes a Func<object>, we can pass a Func<string> because the TResult type placeholder is co-variant and accepts types that are more derived as well: 1: // delegate that's typed to return string. 2: Func<string> stringGenerator = () => DateTime.Now.ToString(); 3:  4: // This will work in .NET 4.0, but not in previous versions 5: Sequence(100, stringGenerator); Previous versions of .NET implemented some forms of co-variance and contra-variance before, but .NET 4.0 goes one step further and allows you to pass or assign an Func<A, BResult> to a Func<Y, ZResult> as long as A is less derived (or same) as Y, and BResult is more derived (or same) as ZResult. Sidebar: The Func and the Predicate A method that takes one argument and returns a bool is generally thought of as a predicate.  Predicates are used to examine an item and determine whether that item satisfies a particular condition.  Predicates are typically unary, but you may also have binary and other predicates as well. Predicates are often used to filter results, such as in the LINQ Where() extension method: 1: var numbers = new[] { 1, 2, 4, 13, 8, 10, 27 }; 2:  3: // call Where() using a predicate which determines if the number is even 4: var evens = numbers.Where(num => num % 2 == 0); As of .NET 3.5, predicates are typically represented as Func<T, bool> where T is the type of the item to examine.  Previous to .NET 3.5, there was a Predicate<T> type that tended to be used (which we’ll discuss next week) and is still supported, but most developers recommend using Func<T, bool> now, as it prevents confusion with overloads that accept unary predicates and binary predicates, etc.: 1: // this seems more confusing as an overload set, because of Predicate vs Func 2: public static SomeMethod(Predicate<int> unaryPredicate) { } 3: public static SomeMethod(Func<int, int, bool> binaryPredicate) { } 4:  5: // this seems more consistent as an overload set, since just uses Func 6: public static SomeMethod(Func<int, bool> unaryPredicate) { } 7: public static SomeMethod(Func<int, int, bool> binaryPredicate) { } Also, even though Predicate<T> and Func<T, bool> match the same signatures, they are separate types!  Thus you cannot assign a Predicate<T> instance to a Func<T, bool> instance and vice versa: 1: // the same method, lambda expression, etc can be assigned to both 2: Predicate<int> isEven = i => (i % 2) == 0; 3: Func<int, bool> alsoIsEven = i => (i % 2) == 0; 4:  5: // but the delegate instances cannot be directly assigned, strongly typed! 6: // ERROR: cannot convert type... 7: isEven = alsoIsEven; 8:  9: // however, you can assign by wrapping in a new instance: 10: isEven = new Predicate<int>(alsoIsEven); 11: alsoIsEven = new Func<int, bool>(isEven); So, the general advice that seems to come from most developers is that Predicate<T> is still supported, but we should use Func<T, bool> for consistency in .NET 3.5 and above. Sidebar: Func as a Generator for Unit Testing One area of difficulty in unit testing can be unit testing code that is based on time of day.  We’d still want to unit test our code to make sure the logic is accurate, but we don’t want the results of our unit tests to be dependent on the time they are run. One way (of many) around this is to create an internal generator that will produce the “current” time of day.  This would default to returning result from DateTime.Now (or some other method), but we could inject specific times for our unit testing.  Generators are typically methods that return (generate) a value for use in a class/method. For example, say we are creating a CacheItem<T> class that represents an item in the cache, and we want to make sure the item shows as expired if the age is more than 30 seconds.  Such a class could look like: 1: // responsible for maintaining an item of type T in the cache 2: public sealed class CacheItem<T> 3: { 4: // helper method that returns the current time 5: private static Func<DateTime> _timeGenerator = () => DateTime.Now; 6:  7: // allows internal access to the time generator 8: internal static Func<DateTime> TimeGenerator 9: { 10: get { return _timeGenerator; } 11: set { _timeGenerator = value; } 12: } 13:  14: // time the item was cached 15: public DateTime CachedTime { get; private set; } 16:  17: // the item cached 18: public T Value { get; private set; } 19:  20: // item is expired if older than 30 seconds 21: public bool IsExpired 22: { 23: get { return _timeGenerator() - CachedTime > TimeSpan.FromSeconds(30.0); } 24: } 25:  26: // creates the new cached item, setting cached time to "current" time 27: public CacheItem(T value) 28: { 29: Value = value; 30: CachedTime = _timeGenerator(); 31: } 32: } Then, we can use this construct to unit test our CacheItem<T> without any time dependencies: 1: var baseTime = DateTime.Now; 2:  3: // start with current time stored above (so doesn't drift) 4: CacheItem<int>.TimeGenerator = () => baseTime; 5:  6: var target = new CacheItem<int>(13); 7:  8: // now add 15 seconds, should still be non-expired 9: CacheItem<int>.TimeGenerator = () => baseTime.AddSeconds(15); 10:  11: Assert.IsFalse(target.IsExpired); 12:  13: // now add 31 seconds, should now be expired 14: CacheItem<int>.TimeGenerator = () => baseTime.AddSeconds(31); 15:  16: Assert.IsTrue(target.IsExpired); Now we can unit test for 1 second before, 1 second after, 1 millisecond before, 1 day after, etc.  Func delegates can be a handy tool for this type of value generation to support more testable code.  Summary Generic delegates give us a lot of power to make truly generic algorithms and classes.  The Func family of delegates is a great way to be able to specify functions to calculate a result based on 0-16 arguments.  Stay tuned in the weeks that follow for other generic delegates in the .NET Framework!   Tweet Technorati Tags: .NET, C#, CSharp, Little Wonders, Generics, Func, Delegates

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  • Collect all extension methods to generic class in another generic class

    - by Hun1Ahpu
    I'd like to create a lot of extension methods for some generic class, e.g. for public class SimpleLinkedList<T> where T:IComparable And I've started creating methods like this: public static class LinkedListExtensions { public static T[] ToArray<T>(this SimpleLinkedList<T> simpleLinkedList) where T:IComparable { //// code } } But when I tried to make LinkedListExtensions class generic like this: public static class LinkedListExtensions<T> where T:IComparable { public static T[] ToArray(this SimpleLinkedList<T> simpleLinkedList) { ////code } } I get "Extension methods can only be declared in non-generic, non-nested static class". And I'm trying to guess where this restriction came from and have no ideas.

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