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• Rails relation select

  - by Dimitar Vouldjeff

  Hi, I have the following models: class User < ActiveRecord::Base has_many :results, :dependent => :destroy has_many :participants, :dependent => :destroy has_many :courses, :through => :participants end class Course < ActiveRecord::Base has_many :tests, :dependent => :destroy has_many :participants, :dependent => :destroy has_many :users, :through => :participants end class Result < ActiveRecord::Base belongs_to :test belongs_to :user end class Test < ActiveRecord::Base belongs_to :course has_many :results, :dependent => :destroy end The Idea is that a user has_and_belongs_to_many courses, the course has_many tests, and every test has_and_belongs_to_many users (results). So what is the best query to select every Result from a single Course (not test), and also the query to select every Result from a single Course, but from one user. Thanks!

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• On Memory Allocation and C++

  - by Arpan

  And I quote from MSDN http://msdn.microsoft.com/en-us/library/aa366533(VS.85).aspx: The malloc function has the disadvantage of being run-time dependent. The new operator has the disadvantage of being compiler dependent and language dependent. Now the questions folks: a) What do we mean that malloc is run-time dependent? What kind of dynamic memory allocation functions can be independent of run-time? This statement sounds real strange. b) new is language dependent? Of course it should be right? Are HeapAlloc, LocalAlloc etc language independent? c) From a pure performance perspective are the MSVC provided routines preferable? Arpan

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• "C variable type sizes are machine dependent." Is it really true? signed & unsigned numbers ;

  - by claws

  Hello, I've been told that C types are machine dependent. Today I wanted to verify it. void legacyTypes() { /* character types */ char k_char = 'a'; //Signedness --> signed & unsigned signed char k_char_s = 'a'; unsigned char k_char_u = 'a'; /* integer types */ int k_int = 1; /* Same as "signed int" */ //Signedness --> signed & unsigned signed int k_int_s = -2; unsigned int k_int_u = 3; //Size --> short, _____, long, long long short int k_s_int = 4; long int k_l_int = 5; long long int k_ll_int = 6; /* real number types */ float k_float = 7; double k_double = 8; } I compiled it on a 32-Bit machine using minGW C compiler _legacyTypes: pushl %ebp movl %esp, %ebp subl $48, %esp movb $97, -1(%ebp) # char movb $97, -2(%ebp) # signed char movb $97, -3(%ebp) # unsigned char movl $1, -8(%ebp) # int movl $-2, -12(%ebp)# signed int movl $3, -16(%ebp) # unsigned int movw $4, -18(%ebp) # short int movl $5, -24(%ebp) # long int movl $6, -32(%ebp) # long long int movl $0, -28(%ebp) movl $0x40e00000, %eax movl %eax, -36(%ebp) fldl LC2 fstpl -48(%ebp) leave ret I compiled the same code on 64-Bit processor (Intel Core 2 Duo) on GCC (linux) legacyTypes: .LFB2: .cfi_startproc pushq %rbp .cfi_def_cfa_offset 16 movq %rsp, %rbp .cfi_offset 6, -16 .cfi_def_cfa_register 6 movb $97, -1(%rbp) # char movb $97, -2(%rbp) # signed char movb $97, -3(%rbp) # unsigned char movl $1, -12(%rbp) # int movl $-2, -16(%rbp)# signed int movl $3, -20(%rbp) # unsigned int movw $4, -6(%rbp) # short int movq $5, -32(%rbp) # long int movq $6, -40(%rbp) # long long int movl $0x40e00000, %eax movl %eax, -24(%rbp) movabsq $4620693217682128896, %rax movq %rax, -48(%rbp) leave ret Observations char, signed char, unsigned char, int, unsigned int, signed int, short int, unsigned short int, signed short int all occupy same no. of bytes on both 32-Bit & 64-Bit Processor. The only change is in long int & long long int both of these occupy 32-bit on 32-bit machine & 64-bit on 64-bit machine. And also the pointers, which take 32-bit on 32-bit CPU & 64-bit on 64-bit CPU. Questions: I cannot say, what the books say is wrong. But I'm missing something here. What exactly does "Variable types are machine dependent mean?" As you can see, There is no difference between instructions for unsigned & signed numbers. Then how come the range of numbers that can be addressed using both is different? I was reading http://stackoverflow.com/questions/2511246/how-to-maintain-fixed-size-of-c-variable-types-over-different-machines I didn't get the purpose of the question or their answers. What maintaining fixed size? They all are the same. I didn't understand how those answers are going to ensure the same size.

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• Couldn't make Angry birds to work on wine

  - by Ashfame

  I could run Notepad++ easily but I fail to run the Angry bird exe. Whenever I open the exe, I see one of my screen flickrs a bit (as lines and not the whole screen) and nothing happens. Any ideas? Edit: Output of wine angrybirds.exe fixme:actctx:parse_depend_manifests Could not find dependent assembly L"Microsoft.VC80.CRT" (8.0.50727.4053) fixme:actctx:parse_depend_manifests Could not find dependent assembly L"Microsoft.VC90.CRT" (9.0.21022.8) err:module:import_dll Library MSVCP90.dll (which is needed by L"C:\\windows\\system32\\AppUpWrapper.dll") not found err:module:import_dll Library AppUpWrapper.dll (which is needed by L"C:\\windows\\system32\\angrybirds.exe") not found err:module:LdrInitializeThunk Main exe initialization for L"C:\\windows\\system32\\angrybirds.exe" failed, status c0000135 I think it didn't even install. I manually dropped those files in the folder but still no gain. Edit: Progress I dropped the file MSVCP90.dll manually and now this is what I get in the output fixme:actctx:parse_depend_manifests Could not find dependent assembly L"Microsoft.VC80.CRT" (8.0.50727.4053) fixme:actctx:parse_depend_manifests Could not find dependent assembly L"Microsoft.VC90.CRT" (9.0.21022.8) fixme:heap:HeapSetInformation 0x541000 0 0x32fd48 4 fixme:heap:HeapSetInformation (nil) 1 (nil) 0 EXCEPTION: Failed to open data/scripts/starLimits.lua wine: Unhandled exception 0x40000015 at address 0x7b880023:0x78b271d0 (thread 0009), starting debugger... fixme:msvcr90:__clean_type_info_names_internal (0x10267694) stub fixme:msvcr90:__clean_type_info_names_internal (0x78506644) stub ashfame@ashfame-desktop:~$ Process of pid=0008 has terminated No process loaded, cannot execute 'echo Modules:' Cannot get info on module while no process is loaded No process loaded, cannot execute 'echo Threads:' process tid prio (all id:s are in hex) 0000000e services.exe 00000014 0 00000010 0 0000000f 0 00000011 winedevice.exe 00000018 0 00000016 0 00000013 0 00000012 0 00000019 explorer.exe 0000001a 0 You must be attached to a process to run this command. No process loaded, cannot execute 'detach' and there the terminal hangs (I mean I would have to Ctrl + C to get out). It shows up the famous message, that it needs to close down. Edit: Just to let you know that I am still stuck at it. I don't use wine for anything else, so I am ready to do a clean install of wine and everything if anyone is willing to provide me instructions.

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• For nodejs what are best design practices for native modules which share dependencies?

  - by Mark Essel

  Hypothetical situation, I have 3 node modules all native, A, B, and C.  A is a utilities module which exposes several functions to javascript through the node interface, in addition it declares/defines a rich set of native structures and functions B is a module which is dependent on data structures and source in A, it exposes some functions to javascript, in addition it declares/defines native structures and functions C is a module which is dependent on data structures and source in A & B, it exploses some functions to javascript, in addition it declares/defines native structures and functions So far when setting up these modules I have a preinstall script to install other dependent includes, but in order to access all of another modules source what is the best way to link to it's share library object (*.node) ? Is there an alternative best practice for native modules (such as installing all source from other modules before building that single module)? Reply

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• Troubleshoot Perl module installation on Mac OS X

  - by Daniel Standage

  I'm trying to install the Perl module Set::IntervalTree on Mac OS X. I recently installed it today on an Ubuntu box with no problem. I simply started cpan, entered install Set:IntervalTree, and it all worked out. However, the installation failed on Mac OS X--it spits out a huge list of compiler errors (below). How would I troubleshoot this. I don't even know where to begin. cpan[1]> install Set::IntervalTree CPAN: Storable loaded ok (v2.18) Going to read /Users/standage/.cpan/Metadata Database was generated on Fri, 14 Jan 2011 02:58:42 GMT CPAN: YAML loaded ok (v0.72) Going to read /Users/standage/.cpan/build/ ............................................................................DONE Found 1 old build, restored the state of 1 Running install for module 'Set::IntervalTree' Running make for B/BE/BENBOOTH/Set-IntervalTree-0.01.tar.gz CPAN: Digest::SHA loaded ok (v5.45) CPAN: Compress::Zlib loaded ok (v2.008) Checksum for /Users/standage/.cpan/sources/authors/id/B/BE/BENBOOTH/Set-IntervalTree-0.01.tar.gz ok Scanning cache /Users/standage/.cpan/build for sizes ............................................................................DONE x Set-IntervalTree-0.01/ x Set-IntervalTree-0.01/src/ x Set-IntervalTree-0.01/src/Makefile x Set-IntervalTree-0.01/src/interval_tree.h x Set-IntervalTree-0.01/src/test_main.cc x Set-IntervalTree-0.01/lib/ x Set-IntervalTree-0.01/lib/Set/ x Set-IntervalTree-0.01/lib/Set/IntervalTree.pm x Set-IntervalTree-0.01/Changes x Set-IntervalTree-0.01/MANIFEST x Set-IntervalTree-0.01/t/ x Set-IntervalTree-0.01/t/Set-IntervalTree.t x Set-IntervalTree-0.01/typemap x Set-IntervalTree-0.01/perlobject.map x Set-IntervalTree-0.01/IntervalTree.xs x Set-IntervalTree-0.01/Makefile.PL x Set-IntervalTree-0.01/README x Set-IntervalTree-0.01/META.yml CPAN: File::Temp loaded ok (v0.18) CPAN.pm: Going to build B/BE/BENBOOTH/Set-IntervalTree-0.01.tar.gz Checking if your kit is complete... Looks good Writing Makefile for Set::IntervalTree cp lib/Set/IntervalTree.pm blib/lib/Set/IntervalTree.pm AutoSplitting blib/lib/Set/IntervalTree.pm (blib/lib/auto/Set/IntervalTree) /usr/bin/perl /System/Library/Perl/5.10.0/ExtUtils/xsubpp -C++ -typemap /System/Library/Perl/5.10.0/ExtUtils/typemap -typemap perlobject.map -typemap typemap IntervalTree.xs > IntervalTree.xsc && mv IntervalTree.xsc IntervalTree.c g++ -c -Isrc -arch x86_64 -arch i386 -arch ppc -g -pipe -fno-common -DPERL_DARWIN -fno-strict-aliasing -I/usr/local/include -g -O0 -DVERSION=\"0.01\" -DXS_VERSION=\"0.01\" "-I/System/Library/Perl/5.10.0/darwin-thread-multi-2level/CORE" -Isrc IntervalTree.c In file included from /usr/include/c++/4.2.1/bits/basic_ios.h:44, from /usr/include/c++/4.2.1/ios:50, from /usr/include/c++/4.2.1/ostream:45, from /usr/include/c++/4.2.1/iostream:45, from IntervalTree.xs:16: /usr/include/c++/4.2.1/bits/locale_facets.h:4420:40: error: macro "do_open" requires 7 arguments, but only 2 given /usr/include/c++/4.2.1/bits/locale_facets.h:4467:34: error: macro "do_close" requires 2 arguments, but only 1 given /usr/include/c++/4.2.1/bits/locale_facets.h:4486:55: error: macro "do_open" requires 7 arguments, but only 2 given /usr/include/c++/4.2.1/bits/locale_facets.h:4513:23: error: macro "do_close" requires 2 arguments, but only 1 given In file included from /usr/include/c++/4.2.1/bits/locale_facets.h:4599, from /usr/include/c++/4.2.1/bits/basic_ios.h:44, from /usr/include/c++/4.2.1/ios:50, from /usr/include/c++/4.2.1/ostream:45, from /usr/include/c++/4.2.1/iostream:45, from IntervalTree.xs:16: /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:58:38: error: macro "do_open" requires 7 arguments, but only 2 given /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:67:71: error: macro "do_open" requires 7 arguments, but only 2 given /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:78:39: error: macro "do_close" requires 2 arguments, but only 1 given In file included from /usr/include/c++/4.2.1/bits/basic_ios.h:44, from /usr/include/c++/4.2.1/ios:50, from /usr/include/c++/4.2.1/ostream:45, from /usr/include/c++/4.2.1/iostream:45, from IntervalTree.xs:16: /usr/include/c++/4.2.1/bits/locale_facets.h:4486: error: ‘do_open’ declared as a ‘virtual’ field /usr/include/c++/4.2.1/bits/locale_facets.h:4486: error: expected ‘;’ before ‘const’ /usr/include/c++/4.2.1/bits/locale_facets.h:4513: error: variable or field ‘do_close’ declared void /usr/include/c++/4.2.1/bits/locale_facets.h:4513: error: expected ‘;’ before ‘const’ In file included from /usr/include/c++/4.2.1/bits/locale_facets.h:4599, from /usr/include/c++/4.2.1/bits/basic_ios.h:44, from /usr/include/c++/4.2.1/ios:50, from /usr/include/c++/4.2.1/ostream:45, from /usr/include/c++/4.2.1/iostream:45, from IntervalTree.xs:16: /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:67: error: expected initializer before ‘const’ /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:78: error: expected initializer before ‘const’ In file included from IntervalTree.xs:19: src/interval_tree.h:95: error: type/value mismatch at argument 1 in template parameter list for ‘template<class _Tp, class _Alloc> class std::vector’ src/interval_tree.h:95: error: expected a type, got ‘IntervalTree<T,N>::it_recursion_node’ src/interval_tree.h:95: error: template argument 2 is invalid src/interval_tree.h: In constructor ‘IntervalTree<T, N>::IntervalTree()’: src/interval_tree.h:130: error: expected type-specifier src/interval_tree.h:130: error: expected `;' src/interval_tree.h:135: error: expected type-specifier src/interval_tree.h:135: error: expected `;' src/interval_tree.h:141: error: request for member ‘push_back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h: In member function ‘void IntervalTree<T, N>::LeftRotate(IntervalTree<T, N>::Node*)’: src/interval_tree.h:178: error: ‘y’ was not declared in this scope src/interval_tree.h: In member function ‘void IntervalTree<T, N>::RightRotate(IntervalTree<T, N>::Node*)’: src/interval_tree.h:240: error: ‘x’ was not declared in this scope src/interval_tree.h: In member function ‘void IntervalTree<T, N>::TreeInsertHelp(IntervalTree<T, N>::Node*)’: src/interval_tree.h:298: error: ‘x’ was not declared in this scope src/interval_tree.h:299: error: ‘y’ was not declared in this scope src/interval_tree.h: In member function ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N)’: src/interval_tree.h:375: error: ‘y’ was not declared in this scope src/interval_tree.h:376: error: ‘x’ was not declared in this scope src/interval_tree.h:377: error: ‘newNode’ was not declared in this scope src/interval_tree.h:379: error: expected type-specifier src/interval_tree.h:379: error: expected `;' src/interval_tree.h: In member function ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::GetSuccessorOf(IntervalTree<T, N>::Node*) const’: src/interval_tree.h:450: error: ‘y’ was not declared in this scope src/interval_tree.h: In member function ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::GetPredecessorOf(IntervalTree<T, N>::Node*) const’: src/interval_tree.h:483: error: ‘y’ was not declared in this scope src/interval_tree.h: In destructor ‘IntervalTree<T, N>::~IntervalTree()’: src/interval_tree.h:546: error: ‘x’ was not declared in this scope src/interval_tree.h:547: error: type/value mismatch at argument 1 in template parameter list for ‘template<class _Tp, class _Alloc> class std::vector’ src/interval_tree.h:547: error: expected a type, got ‘(IntervalTree<T,N>::Node * <expression error>)’ src/interval_tree.h:547: error: template argument 2 is invalid src/interval_tree.h:547: error: invalid type in declaration before ‘;’ token src/interval_tree.h:551: error: request for member ‘push_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:554: error: request for member ‘push_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:557: error: request for member ‘empty’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:558: error: request for member ‘back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:559: error: request for member ‘pop_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:561: error: request for member ‘push_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:564: error: request for member ‘push_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h: In member function ‘void IntervalTree<T, N>::DeleteFixUp(IntervalTree<T, N>::Node*)’: src/interval_tree.h:613: error: ‘w’ was not declared in this scope src/interval_tree.h:614: error: ‘rootLeft’ was not declared in this scope src/interval_tree.h: In member function ‘T IntervalTree<T, N>::remove(IntervalTree<T, N>::Node*)’: src/interval_tree.h:697: error: ‘y’ was not declared in this scope src/interval_tree.h:698: error: ‘x’ was not declared in this scope src/interval_tree.h: In member function ‘std::vector<T, std::allocator<_CharT> > IntervalTree<T, N>::fetch(N, N)’: src/interval_tree.h:819: error: ‘x’ was not declared in this scope src/interval_tree.h:833: error: invalid types ‘int[size_t]’ for array subscript src/interval_tree.h:836: error: request for member ‘push_back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:837: error: request for member ‘back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:838: error: request for member ‘back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:839: error: request for member ‘back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:840: error: request for member ‘size’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:846: error: request for member ‘size’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:847: error: expected `;' before ‘back’ src/interval_tree.h:848: error: request for member ‘pop_back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:850: error: ‘back’ was not declared in this scope src/interval_tree.h:853: error: invalid types ‘int[size_t]’ for array subscript IntervalTree.c: In function ‘void boot_Set__IntervalTree(PerlInterpreter*, CV*)’: IntervalTree.c:365: warning: deprecated conversion from string constant to ‘char*’ src/interval_tree.h: In constructor ‘IntervalTree<T, N>::IntervalTree() [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.c:67: instantiated from here src/interval_tree.h:130: error: cannot convert ‘int*’ to ‘IntervalTree<std::tr1::shared_ptr<sv>, long int>::Node*’ in assignment src/interval_tree.h:135: error: cannot convert ‘int*’ to ‘IntervalTree<std::tr1::shared_ptr<sv>, long int>::Node*’ in assignment ...blah blah blah... ...blah blah blah... ...blah blah blah... ...blah blah blah... ...blah blah blah... ...blah blah blah... src/interval_tree.h:848: error: request for member ‘pop_back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:850: error: ‘back’ was not declared in this scope src/interval_tree.h:853: error: invalid types ‘int[size_t]’ for array subscript IntervalTree.c: In function ‘void boot_Set__IntervalTree(PerlInterpreter*, CV*)’: IntervalTree.c:365: warning: deprecated conversion from string constant to ‘char*’ src/interval_tree.h: In constructor ‘IntervalTree<T, N>::IntervalTree() [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.c:67: instantiated from here src/interval_tree.h:130: error: cannot convert ‘int*’ to ‘IntervalTree<std::tr1::shared_ptr<sv>, long int>::Node*’ in assignment src/interval_tree.h:135: error: cannot convert ‘int*’ to ‘IntervalTree<std::tr1::shared_ptr<sv>, long int>::Node*’ in assignment src/interval_tree.h: In member function ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.xs:57: instantiated from here src/interval_tree.h:375: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:375: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h:376: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:376: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h:377: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:377: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h: In member function ‘std::vector<T, std::allocator<_CharT> > IntervalTree<T, N>::fetch(N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.xs:65: instantiated from here src/interval_tree.h:819: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:819: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant IntervalTree.xs:65: instantiated from here src/interval_tree.h:847: error: dependent-name ‘IntervalTree<T,N>::it_recursion_node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:847: note: say ‘typename IntervalTree<T,N>::it_recursion_node’ if a type is meant src/interval_tree.h: In destructor ‘IntervalTree<T, N>::~IntervalTree() [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.c:205: instantiated from here src/interval_tree.h:546: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:546: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h: In member function ‘void IntervalTree<T, N>::TreeInsertHelp(IntervalTree<T, N>::Node*) [with T = std::tr1::shared_ptr<sv>, N = long int]’: src/interval_tree.h:380: instantiated from ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’ IntervalTree.xs:57: instantiated from here src/interval_tree.h:298: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:298: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h:299: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:299: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h: In member function ‘void IntervalTree<T, N>::LeftRotate(IntervalTree<T, N>::Node*) [with T = std::tr1::shared_ptr<sv>, N = long int]’: src/interval_tree.h:395: instantiated from ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’ IntervalTree.xs:57: instantiated from here src/interval_tree.h:178: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:178: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h: In member function ‘void IntervalTree<T, N>::RightRotate(IntervalTree<T, N>::Node*) [with T = std::tr1::shared_ptr<sv>, N = long int]’: src/interval_tree.h:399: instantiated from ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’ IntervalTree.xs:57: instantiated from here src/interval_tree.h:240: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:240: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant lipo: can't open input file: /var/tmp//ccLthuaw.out (No such file or directory) make: *** [IntervalTree.o] Error 1 BENBOOTH/Set-IntervalTree-0.01.tar.gz make -- NOT OK Running make test Can't test without successful make Running make install Make had returned bad status, install seems impossible Failed during this command: BENBOOTH/Set-IntervalTree-0.01.tar.gz : make NO

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• Passing two variables to separate table...associations problem

  - by bgadoci

  I have developed an application and I seem to be having some problems with my associations. I have the following: class User < ActiveRecord::Base acts_as_authentic has_many :questions, :dependent => :destroy has_many :sites , :dependent => :destroy end Questions class Question < ActiveRecord::Base has_many :sites, :dependent => :destroy has_many :notes, :through => :sites belongs_to :user end Sites (think of this as answers to questions) class Site < ActiveRecord::Base acts_as_voteable :vote_counter => true belongs_to :question belongs_to :user has_many :notes, :dependent => :destroy has_many :likes, :dependent => :destroy has_attached_file :photo, :styles => { :small => "250x250>" } validates_presence_of :name, :description end When a Site (answer) is created I am successfully passing the question_id to the Sites table but I can't figure out how to also pass the user_id. Here is my SitesController#create def create @question = Question.find(params[:question_id]) @site = @question.sites.create!(params[:site]) respond_to do |format| format.html { redirect_to(@question) } format.js end end

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• How to remove Modules from a Intellij Maven Project permanently?

  - by herpnderpn

  I am currently working on a larger scale Maven-based project in IntelliJIdea 12.1.6 Ultimate. I have been working with IntelliJIdea since about 5 months. An included module has dependencies on another module. The dependent module's source was also part of my project until recently. Since I removed the dependent module from my project, I get compile errors whenever I am trying to compile the source without maven. The pom.xml of removed modules in Intellij seem to be placed onto the Settings-Maven-Ignored Files. I cant seem to remove it from there, only check or uncheck it. It's not possible to include the module again since IntelliJ will say its still under Ignored Files. 2 ways allow me to compile again: Uncheck the pom from Ignored files, which will include the module again in my project. Or delete the source of the dependent project, so my project will load the dependent module from the maven repository. But whenever I update my project from svn, the source of the dependent module is restored (I don't know why this even happens since its not part my project) and the cycle begins anew. I googled this for a while since it gets really annoying. It became a problem with several excluded modules. I could rebuild the intellij-project but since a lot of IntelliJ settings were made (not related to the problem) I would rather solve this. Any help is appreciated, I guess I must be missing something

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• Rails Association issue with NoMethodError in event_controller

  - by pmanning

  Kinda a noob trying to understand I think I need to define rsvps but not sure what to put... I'm trying to add a Join/Unjoin button to user created Events, similar to a Follow/Unfollow button for Users. NoMethodError in Events#show undefined method `model_name' for NilClass:Class in line #1 _unjoin.html.erb 1: <%= form_for(current_user.rsvps.find_by_joined_id(@event), 2: html: { method: :delete }) do |f| %> 3: <%= f.submit "Leave", class: "btn btn-large" %> 4: <% end %> events_controller.rb def show @event = Event.find(params[:id]) @user = current_user end Here's the models rsvp.rb class Rsvp < ActiveRecord::Base attr_accessible :joined_id belongs_to :joiner, class_name: "User" belongs_to :joined, class_name: "User" validates :joiner_id, presence: true validates :joined_id, presence: true end user.rb has_many :rsvps, foreign_key: "joiner_id", dependent: :destroy has_many :joined_events, through: :rsvps, source: :joined has_many :reverse_rsvps, foreign_key: "joined_id", class_name: "Rsvp", dependent: :destroy has_many :joiners, through: :reverse_rsvps, source: :joiner event.rb belongs_to :user has_many :rsvps, foreign_key: "joiner_id", dependent: :destroy has_many :joined_events, through: :rsvps, source: :joined has_many :reverse_rsvps, foreign_key: "joined_id", class_name: "Rsvp", dependent: :destroy has_many :joiners, through: :reverse_rsvps, source: :joiner

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• Maven workspace resolution horked

  - by user237815

  I'm using m2eclipse to manage maven projects. Somehow I did a bad thing, and now the system is behaving as if workspace resolution is disabled. I have several projects that depend on a main project. This project has a version of 4.0-SNAPSHOT, and all the dependent projects reference it in the dependencies section of their poms. Everything was working fine until I created an entirely new project and mistakenly copied the pom from the main project into the new project. Suddenly, all of the dependent projects got the error: "The container 'Maven Dependencies" references non existing library C:\users\myusername.m2\com\mydomain\myproject\4.0-SNAPSHOT\myproject-4.0-SNAPSHOT.jar I zapped the offending new project, but the error remains for all the dependent projects. I've made no changes (to my knowledge) in the main project or any of the dependent projects, so I'm guessing something got changed in the Eclipse environment. Does m2eclipse or Maven itself maintain settings anywhere that I can blow away?

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• jQuery, Forms, Browser Refreshes

  - by Eric Cope

  I have a large form with some fields values dependent on previous elements. I use jquery's .trigger event to trigger the dependent field's update functions. When I refresh the page (click reload or click back), the previous values selected are still there, but the dependent fields are not reflecting the other element's values. How can I trigger the update functions upon refresh? I saw a way to prevent the browser from using the form's cached values. I'd rather use the cached values and update the elements dependent on the elements with cached values.

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• Back to Basics: When does a .NET Assembly Dependency get loaded

  - by Rick Strahl

  When we work on typical day to day applications, it's easy to forget some of the core features of the .NET framework. For me personally it's been a long time since I've learned about some of the underlying CLR system level services even though I rely on them on a daily basis. I often think only about high level application constructs and/or high level framework functionality, but the low level stuff is often just taken for granted. Over the last week at DevConnections I had all sorts of low level discussions with other developers about the inner workings of this or that technology (especially in light of my Low Level ASP.NET Architecture talk and the Razor Hosting talk). One topic that came up a couple of times and ended up a point of confusion even amongst some seasoned developers (including some folks from Microsoft <snicker>) is when assemblies actually load into a .NET process. There are a number of different ways that assemblies are loaded in .NET. When you create a typical project assemblies usually come from: The Assembly reference list of the top level 'executable' project The Assembly references of referenced projects Dynamically loaded at runtime via AppDomain/Reflection loading In addition .NET automatically loads mscorlib (most of the System namespace) the boot process that hosts the .NET runtime in EXE apps, or some other kind of runtime hosting environment (runtime hosting in servers like IIS, SQL Server or COM Interop). In hosting environments the runtime host may also pre-load a bunch of assemblies on its own (for example the ASP.NET host requires all sorts of assemblies just to run itself, before ever routing into your user specific code). Assembly Loading The most obvious source of loaded assemblies is the top level application's assembly reference list. You can add assembly references to a top level application and those assembly references are then available to the application. In a nutshell, referenced assemblies are not immediately loaded - they are loaded on the fly as needed. So regardless of whether you have an assembly reference in a top level project, or a dependent assembly assemblies typically load on an as needed basis, unless explicitly loaded by user code. The same is true of dependent assemblies. To check this out I ran a simple test: I have a utility assembly Westwind.Utilities which is a general purpose library that can work in any type of project. Due to a couple of small requirements for encoding and a logging piece that allows logging Web content (dependency on HttpContext.Current) this utility library has a dependency on System.Web. Now System.Web is a pretty large assembly and generally you'd want to avoid adding it to a non-Web project if it can be helped. So I created a Console Application that loads my utility library: You can see that the top level Console app a reference to Westwind.Utilities and System.Data (beyond the core .NET libs). The Westwind.Utilities project on the other hand has quite a few dependencies including System.Web. I then add a main program that accesses only a simple utillity method in the Westwind.Utilities library that doesn't require any of the classes that access System.Web: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.ReadLine(); } StringUtils.NewStringId() calls into Westwind.Utilities, but it doesn't rely on System.Web. Any guesses what the assembly list looks like when I stop the code on the ReadLine() command? I'll wait here while you think about it… … … So, when I stop on ReadLine() and then fire up Process Explorer and check the assembly list I get: We can see here that .NET has not actually loaded any of the dependencies of the Westwind.Utilities assembly. Also not loaded is the top level System.Data reference even though it's in the dependent assembly list of the top level project. Since this particular function I called only uses core System functionality (contained in mscorlib) there's in fact nothing else loaded beyond the main application and my Westwind.Utilities assembly that contains the method accessed. None of the dependencies of Westwind.Utilities loaded. If you were to open the assembly in a disassembler like Reflector or ILSpy, you would however see all the compiled in dependencies. The referenced assemblies are in the dependency list and they are loadable, but they are not immediately loaded by the application. In other words the C# compiler and .NET linker are smart enough to figure out the dependencies based on the code that actually is referenced from your application and any dependencies cascading down into the dependencies from your top level application into the referenced assemblies. In the example above the usage requirement is pretty obvious since I'm only calling a single static method and then exiting the app, but in more complex applications these dependency relationships become very complicated - however it's all taken care of by the compiler and linker figuring out what types and members are actually referenced and including only those assemblies that are in fact referenced in your code or required by any of your dependencies. The good news here is: That if you are referencing an assembly that has a dependency on something like System.Web in a few places that are not actually accessed by any of your code or any dependent assembly code that you are calling, that assembly is never loaded into memory! Some Hosting Environments pre-load Assemblies The load behavior can vary however. In Console and desktop applications we have full control over assembly loading so we see the core CLR behavior. However other environments like ASP.NET for example will preload referenced assemblies explicitly as part of the startup process - primarily to minimize load conflicts. Specifically ASP.NET pre-loads all assemblies referenced in the assembly list and the /bin folder. So in Web applications it definitely pays to minimize your top level assemblies if they are not used. Understanding when Assemblies Load To clarify and see it actually happen what I described in the first example , let's look at a couple of other scenarios. To see assemblies loading at runtime in real time lets create a utility function to print out loaded assemblies to the console: public static void PrintAssemblies() { var assemblies = AppDomain.CurrentDomain.GetAssemblies(); foreach (var assembly in assemblies) { Console.WriteLine(assembly.GetName()); } } Now let's look at the first scenario where I have class method that references internally uses System.Web. In the first scenario lets add a method to my main program like this: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.ReadLine(); PrintAssemblies(); } public static void WebLogEntry() { var entry = new WebLogEntry(); entry.UpdateFromRequest(); Console.WriteLine(entry.QueryString); } UpdateFromWebRequest() internally accesses HttpContext.Current to read some information of the ASP.NET Request object so it clearly needs a reference System.Web to work. In this first example, the method that holds the calling code is never called, but exists as a static method that can potentially be called externally at some point. What do you think will happen here with the assembly loading? Will System.Web load in this example? No - it doesn't. Because the WebLogEntry() method is never called by the mainline application (or anywhere else) System.Web is not loaded. .NET dynamically loads assemblies as code that needs it is called. No code references the WebLogEntry() method and so System.Web is never loaded. Next, let's add the call to this method, which should trigger System.Web to be loaded because a dependency exists. Let's change the code to: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.WriteLine("--- Before:"); PrintAssemblies(); WebLogEntry(); Console.WriteLine("--- After:"); PrintAssemblies(); Console.ReadLine(); } public static void WebLogEntry() { var entry = new WebLogEntry(); entry.UpdateFromRequest(); Console.WriteLine(entry.QueryString); } Looking at the code now, when do you think System.Web will be loaded? Will the before list include it? Yup System.Web gets loaded, but only after it's actually referenced. In fact, just until before the call to UpdateFromRequest() System.Web is not loaded - it only loads when the method is actually called and requires the reference in the executing code. Moral of the Story So what have we learned - or maybe remembered again? Dependent Assembly References are not pre-loaded when an application starts (by default) Dependent Assemblies that are not referenced by executing code are never loaded Dependent Assemblies are just in time loaded when first referenced in code All of this is nothing new - .NET has always worked like this. But it's good to have a refresher now and then and go through the exercise of seeing it work in action. It's not one of those things we think about everyday, and as I found out last week, I couldn't remember exactly how it worked since it's been so long since I've learned about this. And apparently I'm not the only one as several other people I had discussions with in relation to loaded assemblies also didn't recall exactly what should happen or assumed incorrectly that just having a reference automatically loads the assembly. The moral of the story for me is: Trying at all costs to eliminate an assembly reference from a component is not quite as important as it's often made out to be. For example, the Westwind.Utilities module described above has a logging component, including a Web specific logging entry that supports pulling information from the active HTTP Context. Adding that feature requires a reference to System.Web. Should I worry about this in the scope of this library? Probably not, because if I don't use that one class of nearly a hundred, System.Web never gets pulled into the parent process. IOW, System.Web only loads when I use that specific feature and if I am, well I clearly have to be running in a Web environment anyway to use it realistically. The alternative would be considerably uglier: Pulling out the WebLogEntry class and sticking it into another assembly and breaking up the logging code. In this case - definitely not worth it. So, .NET definitely goes through some pretty nifty optimizations to ensure that it loads only what it needs and in most cases you can just rely on .NET to do the right thing. Sometimes though assembly loading can go wrong (especially when signed and versioned local assemblies are involved), but that's subject for a whole other post…© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  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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• How can I remove python 2.7 after installing python 3.3?

  - by phoenix bai

  I have successfully installed python 3.3 on Ubuntu 12.10. Since I don’t need multiple versions of python, I want to remove the existing python 2.7. When I try to do that, using sudo apt-get remove python2.7 Ubuntu warns me that there are tons of system dependent components which will also be removed. It looks really scary. So, is there a way to remove python 2.7 without removing the system dependent components, or can I direct those dependents to use python 3.3?

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• Nagios state transition and event handler issue

  - by Dattatray

  We are using Nagios to check duplicate processes. define service { use local-service host_name xxx service_description xxx Duplicate Processes check_interval 1 max_check_attempts 1 contact_groups admins event_handler restart-dependent-processes check_command check_procs_duplicate!2!3!2!2!2 } check_procs_duplicate checks if there are any duplicate processes and returns the state - e.g. CRITICAL. The event handler kills the duplicate processes and it's dependent processes and starts one instance of the process and dependent process. At the end of this again Nagios checks if there are any duplicate processes and sets the state accordingly - OK/WARNING/CRITICAL. The event handler takes more time to start the processes and during this time if someone manually starts the process, the state will remain in CRITICAL itself. During the next interval, Nagios will again check for duplicate processes and it will find it again CRITICAL. The event handler will not get executed now, as the previos and current both the states are CRITICAL. Any pointers about how to fix this issue?

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• Understanding UML composition better

  - by Prog

  The technical difference between Composition and Aggregation in UML (and sometimes in programming too) is that with Composition, the lifetime of the objects composing the composite (e.g. an engine and a steering wheel in a car) is dependent on the composite object. While with Aggregation, the lifetime of the objects making up the composite is independent of the composite. However I'm not sure about something related to composition in UML. Say ClassA is composed of an object of ClassB: class ClassA{ ClassB bInstance; public ClassA(){ bInstance = new ClassB(); } } This is an example of composition, because bInstance is dependent on the lifetime of it's enclosing object. However, regarding UML notation - I'm not sure if I would notate the relationship between ClassA and ClassB with a filled diamond (composition) or a white diamond (aggregation). This is because while the lifetime of some ClassB instances is dependent of ClassA instances - there could be ClassB instances anywhere else in the program - not only within ClassA instances. The question is: if ClassA objects are composed of ClassB objects - but other ClassB objects are free to be used anywhere else in the program: Should the relationship between ClassA and ClassB be notated as aggregation or as composition?

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• Coping with build order requirements in automated builds

  - by Derecho

  I have three Scala packages being built as separate sbt projects in separate repos with a dependency graph like this: M---->D ^ ^ | | +--+--+ ^ | S S is a service. M is a set of message classes shared between S and another service. D is a DAL used by S and the other service, and some of its model appears in the shared messages. If I make a breaking change to all three, and push them up to my Git repo, a build of S will be kicked off in Jenkins. The build will only be successful if, when S is pushed, M and D have already been pushed. Otherwise, Jenkins will find it doesn't have the right dependent package versions available. Even pushing them simultaneously wouldn't be enough -- the dependencies would have to be built and published before the dependent job was even started. Making the jobs dependent in Jenkins isn't enough, because that would just cause the previous version to be built, resulting in an artifact that doesn't have the needed version. Is there a way to set things up so that I don't have to remember to push things in the right order? The only way I can see it working is if there was a way that a build could go into a pending state if its dependencies weren't available yet. I feel like there's a simple solution I'm missing. Surely people deal with this a lot?

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• Webservices error for dev.virtualearth.net/webservices/geocode

  - by Xaisoft

  I am getting the following stacktrace and have no idea what I am looking at and how to debug and fix it: Here is the error: Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. Parser Error Message: Reference.svcmap: Failed to generate code for the service reference 'GeocodeService'. Cannot import wsdl:portType Detail: An exception was thrown while running a WSDL import extension: System.ServiceModel.Description.DataContractSerializerMessageContractImporter Error: Could not load file or assembly 'System.Xml, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' or one of its dependencies. The system cannot find the file specified. XPath to Error Source: //wsdl:definitions[@targetNamespace='http//dev.virtualearth.net /webservices/v1/geocode/contracts']/wsdl:portType[@name='IGeocodeService'] Cannot import wsdl:binding Detail: There was an error importing a wsdl:portType that the wsdl:binding is dependent on. XPath to wsdl:portType: //wsdl:definitions[@targetNamespace='http: //dev.virtualearth.net/webservices/v1/geocode/contracts'] /wsdl:portType[@name='IGeocodeService'] XPath to Error Source: //wsdl:definitions[@targetNamespace='http: //dev.virtualearth.net /webservices/v1/geocode']/wsdl:binding[@name='BasicHttpBinding_IGeocodeService'] Cannot import wsdl:port Detail: There was an error importing a wsdl:binding that the wsdl:port is dependent on. XPath to wsdl:binding: //wsdl:definitions[@targetNamespace='http://dev.virtualearth.net /webservices/v1/geocode']/wsdl:binding[@name='BasicHttpBinding_IGeocodeService'] XPath to Error Source: //wsdl:definitions[@targetNamespace='http://dev.virtualearth.net /webservices/v1/geocode']/wsdl:service[@name='GeocodeService'] /wsdl:port[@name='BasicHttpBinding_IGeocodeService'] Cannot import wsdl:binding Detail: There was an error importing a wsdl:portType that the wsdl:binding is dependent on. XPath to wsdl:portType: //wsdl:definitions[@targetNamespace='http: //dev.virtualearth.net/webservices/v1/geocode/contracts'] /wsdl:portType[@name='IGeocodeService'] XPath to Error Source: //wsdl:definitions[@targetNamespace='http: //dev.virtualearth.net /webservices/v1/geocode']/wsdl:binding[@name='CustomBinding_IGeocodeService'] Cannot import wsdl:port Detail: There was an error importing a wsdl:binding that the wsdl:port is dependent on. XPath to wsdl:binding: //wsdl:definitions[@targetNamespace='http://dev.virtualearth.net /webservices/v1/geocode']/wsdl:binding[@name='CustomBinding_IGeocodeService'] XPath to Error Source: //wsdl:definitions[@targetNamespace='http://dev.virtualearth.net /webservices/v1/geocode']/wsdl:service[@name='GeocodeService'] /wsdl:port[@name='CustomBinding_IGeocodeService']

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• Application/Server dependency mapping

  - by David Stratton

  I'm just curious as to whether such as tool exists (free, open source, or commercial but for a reasonable price) before I build it myself. We're looking for a simple solution to simplify taking web apps online and offline when a server is undergoing maintenance. The idea is that we be able to mark a server as unavailable, and then mark all dependent (direct and indirect) as offline. Our first proof-of-concept is running, and we created an aspx page that lists various applications that have an App_Offline.html file with a friendly "Down for Maintenance" message in a GridView. In the GridView, each app has a LinkButton that, when clicked, either renames the App_Offline.htm to App_Offline.html or vice-versa to take the app online and offline. The next step is to set up all of our dependencies. For example, our store locater would be dependent on our web services, which in turn are dependent on our SQL Server. (that's a simple example. We can easily have several layers, or one app dependent on multiple servers, etc.) In this example, if the SQL server goes down, we would need to drill down recursively to find all apps that depend on it, and then turn them off and on by renaming the App_Offline file appropriately. I realize this will be relatively simple to build, but could be complex to manage. I'm sure we're not the first team to think of this concept, and I'm wondering if there are any open source tools, or if any of you have done something similar and can help us avoid pitfalls. Edit - Update I found the category of software I'm looking for. it's called CMDB - (Configuration Management Database), and it's generally more of a Network Admin type tool than a developer tool. I found some open source products in this category, but none written in .NET. I had considered moving this question to ServerFault.com when I realized I was looking for a netowrk Admin type tool, but since I'm looking for code and a modifiable solution I'll keep the question here.

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• Rails: Multiple "has_many through" for the two same models?

  - by neezer

  Can't wrap my head around this... class User < ActiveRecord::Base has_many :fantasies, :through => :fantasizings has_many :fantasizings, :dependent => :destroy end class Fantasy < ActiveRecord::Base has_many :users, :through => :fantasizings has_many :fantasizings, :dependent => :destroy end class Fantasizing < ActiveRecord::Base belongs_to :user belongs_to :fantasy end ... which works fine for my primary relationship, in that a User can have many Fantasies, and that a Fantasy can belong to many Users. However, I need to add another relationship for liking (as in, a User "likes" a Fantasy rather than "has" it... think of Facebook and how you can "like" a wall-post, even though it doesn't "belong" to you... in fact, the Facebook example is almost exactly what I'm aiming for). I gathered that I should make another association, but I'm kinda confused as to how I might use it, or if this is even the right approach. I started by adding the following: class Fantasy < ActiveRecord::Base ... has_many :users, :through => :approvals has_many :approvals, :dependent => :destroy end class User < ActiveRecord::Base ... has_many :fantasies, :through => :approvals has_many :approvals, :dependent => :destroy end class Approval < ActiveRecord::Base belongs_to :user belongs_to :fantasy end ... but how do I create the association through Approval rather than through Fantasizing? If someone could set me straight on this, I'd be much obliged!

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• Rails Polymorphic Association with multiple associations on the same model

  - by Matt Rogish

  My question is essentially the same as this one: http://stackoverflow.com/questions/1168047/polymorphic-association-with-multiple-associations-on-the-same-model However, the proposed/accepted solution does not work, as illustrated by a commenter later. I have a Photo class that is used all over my app. A post can have a single photo. However, I want to re-use the polymorphic relationship to add a secondary photo. Before: class Photo belongs_to :attachable, :polymorphic => true end class Post has_one :photo, :as => :attachable, :dependent => :destroy end Desired: class Photo belongs_to :attachable, :polymorphic => true end class Post has_one :photo, :as => :attachable, :dependent => :destroy has_one :secondary_photo, :as => :attachable, :dependent => :destroy end However, this fails as it cannot find the class "SecondaryPhoto". Based on what I could tell from that other thread, I'd want to do: has_one :secondary_photo, :as => :attachable, :class_name => "Photo", :dependent => :destroy Except calling Post#secondary_photo simply returns the same photo that is attached via the Photo association, e.g. Post#photo === Post#secondary_photo. Looking at the SQL, it does WHERE type = "Photo" instead of, say, "SecondaryPhoto" as I'd like... Thoughts? Thanks!

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• XML parsing by DOM

  - by blackpearl

  NodeList nList2 = doc.getElementsByTagName("dep"); Map<String, List<Map<String, String>>> depMap = new HashMap<String, List<Map<String, String>>>(); for (int temp = 0; temp < nList2.getLength(); temp++) { Element el = (Element)nList2.item(temp); String type=el.getAttribute("type"); Node nNode = nList2.item(temp); if (nNode.getNodeType() == Node.ELEMENT_NODE) { Element eElement = (Element) nNode; List<Map<String,String>> depList = new ArrayList<Map<String,String>>(); String governor = getTagValue("governor", eElement); String dependent = getTagValue("dependent", eElement); Map<String, String> govdepmap = new HashMap<String, String>(); govdepmap.put(governor, dependent); depList.add(govdepmap); List<Map<String,String>> flist = new ArrayList<Map<String,String>>(); flist.add(govdepmap); depMap.put(type, flist); } } I have the following structure in my XML file: going I Now i want to store the "idx" attribute of each "governor" and "dependent" tag. What code should I change or add?

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• Rails active record association problem

  - by Harm de Wit

  Hello, I'm new at active record association in rails so i don't know how to solve the following problem: I have a tables called 'meetings' and 'users'. I have correctly associated these two together by making a table 'participants' and set the following association statements: class Meeting < ActiveRecord::Base has_many :participants, :dependent => :destroy has_many :users, :through => :participants and class Participant < ActiveRecord::Base belongs_to :meeting belongs_to :user and the last model class User < ActiveRecord::Base has_many :participants, :dependent => :destroy At this point all is going well and i can access the user values of attending participants of a specific meeting by calling @meeting.users in the normal meetingshow.html.erb view. Now i want to make connections between these participants. Therefore i made a model called 'connections' and created the columns of 'meeting_id', 'user_id' and 'connected_user_id'. So these connections are kinda like friendships within a certain meeting. My question is: How can i set the model associations so i can easily control these connections? I would like to see a solution where i could use @meeting.users.each do |user| user.connections.each do |c| <do something> end end I tried this by changing the model of meetings to this: class Meeting < ActiveRecord::Base has_many :participants, :dependent => :destroy has_many :users, :through => :participants has_many :connections, :dependent => :destroy has_many :participating_user_connections, :through => :connections, :source => :user Please, does anyone have a solution/tip how to solve this the rails way?

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• Flow-Design Cheat Sheet &ndash; Part I, Notation

  - by Ralf Westphal

  You want to avoid the pitfalls of object oriented design? Then this is the right place to start. Use Flow-Oriented Analysis (FOA) and –Design (FOD or just FD for Flow-Design) to understand a problem domain and design a software solution. Flow-Orientation as described here is related to Flow-Based Programming, Event-Based Programming, Business Process Modelling, and even Event-Driven Architectures. But even though “thinking in flows” is not new, I found it helpful to deviate from those precursors for several reasons. Some aim at too big systems for the average programmer, some are concerned with only asynchronous processing, some are even not very much concerned with programming at all. What I was looking for was a design method to help in software projects of any size, be they large or tiny, involing synchronous or asynchronous processing, being local or distributed, running on the web or on the desktop or on a smartphone. That´s why I took ideas from all of the above sources and some additional and came up with Event-Based Components which later got repositioned and renamed to Flow-Design. In the meantime this has generated some discussion (in the German developer community) and several teams have started to work with Flow-Design. Also I´ve conducted quite some trainings using Flow-Orientation for design. The results are very promising. Developers find it much easier to design software using Flow-Orientation than OOAD-based object orientation. Since Flow-Orientation is moving fast and is not covered completely by a single source like a book, demand has increased for at least an overview of the current state of its notation. This page is trying to answer this demand by briefly introducing/describing every notational element as well as their translation into C# source code. Take this as a cheat sheet to put next to your whiteboard when designing software. However, please do not expect any explanation as to the reasons behind Flow-Design elements. Details on why Flow-Design at all and why in this specific way you´ll find in the literature covering the topic. Here´s a resource page on Flow-Design/Event-Based Components, if you´re able to read German. Notation Connected Functional Units The basic element of any FOD are functional units (FU): Think of FUs as some kind of software code block processing data. For the moment forget about classes, methods, “components”, assemblies or whatever. See a FU as an abstract piece of code. Software then consists of just collaborating FUs. I´m using circles/ellipses to draw FUs. But if you like, use rectangles. Whatever suites your whiteboard needs best.   The purpose of FUs is to process input and produce output. FUs are transformational. However, FUs are not called and do not call other FUs. There is no dependency between FUs. Data just flows into a FU (input) and out of it (output). From where and where to is of no concern to a FU.   This way FUs can be concatenated in arbitrary ways:   Each FU can accept input from many sources and produce output for many sinks:   Flows Connected FUs form a flow with a start and an end. Data is entering a flow at a source, and it´s leaving it through a sink. Think of sources and sinks as special FUs which conntect wires to the environment of a network of FUs.   Wiring Details Data is flowing into/out of FUs through wires. This is to allude to electrical engineering which since long has been working with composable parts. Wires are attached to FUs usings pins. They are the entry/exit points for the data flowing along the wires. Input-/output pins currently need not be drawn explicitly. This is to keep designing on a whiteboard simple and quick.   Data flowing is of some type, so wires have a type attached to them. And pins have names. If there is only one input pin and output pin on a FU, though, you don´t need to mention them. The default is Process for a single input pin, and Result for a single output pin. But you´re free to give even single pins different names.   There is a shortcut in use to address a certain pin on a destination FU:   The type of the wire is put in parantheses for two reasons. 1. This way a “no-type” wire can be easily denoted, 2. this is a natural way to describe tuples of data.   To describe how much data is flowing, a star can be put next to the wire type:   Nesting – Boards and Parts If more than 5 to 10 FUs need to be put in a flow a FD starts to become hard to understand. To keep diagrams clutter free they can be nested. You can turn any FU into a flow: This leads to Flow-Designs with different levels of abstraction. A in the above illustration is a high level functional unit, A.1 and A.2 are lower level functional units. One of the purposes of Flow-Design is to be able to describe systems on different levels of abstraction and thus make it easier to understand them. Humans use abstraction/decomposition to get a grip on complexity. Flow-Design strives to support this and make levels of abstraction first class citizens for programming. You can read the above illustration like this: Functional units A.1 and A.2 detail what A is supposed to do. The whole of A´s responsibility is decomposed into smaller responsibilities A.1 and A.2. FU A thus does not do anything itself anymore! All A is responsible for is actually accomplished by the collaboration between A.1 and A.2. Since A now is not doing anything anymore except containing A.1 and A.2 functional units are devided into two categories: boards and parts. Boards are just containing other functional units; their sole responsibility is to wire them up. A is a board. Boards thus depend on the functional units nested within them. This dependency is not of a functional nature, though. Boards are not dependent on services provided by nested functional units. They are just concerned with their interface to be able to plug them together. Parts are the workhorses of flows. They contain the real domain logic. They actually transform input into output. However, they do not depend on other functional units. Please note the usage of source and sink in boards. They correspond to input-pins and output-pins of the board.   Implicit Dependencies Nesting functional units leads to a dependency tree. Boards depend on nested functional units, they are the inner nodes of the tree. Parts are independent, they are the leafs: Even though dependencies are the bane of software development, Flow-Design does not usually draw these dependencies. They are implicitly created by visually nesting functional units. And they are harmless. Boards are so simple in their functionality, they are little affected by changes in functional units they are depending on. But functional units are implicitly dependent on more than nested functional units. They are also dependent on the data types of the wires attached to them: This is also natural and thus does not need to be made explicit. And it pertains mainly to parts being dependent. Since boards don´t do anything with regard to a problem domain, they don´t care much about data types. Their infrastructural purpose just needs types of input/output-pins to match.   Explicit Dependencies You could say, Flow-Orientation is about tackling complexity at its root cause: that´s dependencies. “Natural” dependencies are depicted naturally, i.e. implicitly. And whereever possible dependencies are not even created. Functional units don´t know their collaborators within a flow. This is core to Flow-Orientation. That makes for high composability of functional units. A part is as independent of other functional units as a motor is from the rest of the car. And a board is as dependend on nested functional units as a motor is on a spark plug or a crank shaft. With Flow-Design software development moves closer to how hardware is constructed. Implicit dependencies are not enough, though. Sometimes explicit dependencies make designs easier – as counterintuitive this might sound. So FD notation needs a ways to denote explicit dependencies: Data flows along wires. But data does not flow along dependency relations. Instead dependency relations represent service calls. Functional unit C is depending on/calling services on functional unit S. If you want to be more specific, name the services next to the dependency relation: Although you should try to stay clear of explicit dependencies, they are fundamentally ok. See them as a way to add another dimension to a flow. Usually the functionality of the independent FU (“Customer repository” above) is orthogonal to the domain of the flow it is referenced by. If you like emphasize this by using different shapes for dependent and independent FUs like above. Such dependencies can be used to link in resources like databases or shared in-memory state. FUs can not only produce output but also can have side effects. A common pattern for using such explizit dependencies is to hook a GUI into a flow as the source and/or the sink of data: Which can be shortened to: Treat FUs others depend on as boards (with a special non-FD API the dependent part is connected to), but do not embed them in a flow in the diagram they are depended upon.   Attributes of Functional Units Creation and usage of functional units can be modified with attributes. So far the following have shown to be helpful: Singleton: FUs are by default multitons. FUs in the same of different flows with the same name refer to the same functionality, but to different instances. Think of functional units as objects that get instanciated anew whereever they appear in a design. Sometimes though it´s helpful to reuse the same instance of a functional unit; this is always due to valuable state it holds. Signify this by annotating the FU with a “(S)”. Multiton: FUs on which others depend are singletons by default. This is, because they usually are introduced where shared state comes into play. If you want to change them to be a singletons mark them with a “(M)”. Configurable: Some parts need to be configured before the can do they work in a flow. Annotate them with a “(C)” to have them initialized before any data items to be processed by them arrive. Do not assume any order in which FUs are configured. How such configuration is happening is an implementation detail. Entry point: In each design there needs to be a single part where “it all starts”. That´s the entry point for all processing. It´s like Program.Main() in C# programs. Mark the entry point part with an “(E)”. Quite often this will be the GUI part. How the entry point is started is an implementation detail. Just consider it the first FU to start do its job.   Patterns / Standard Parts If more than a single wire is attached to an output-pin that´s called a split (or fork). The same data is flowing on all of the wires. Remember: Flow-Designs are synchronous by default. So a split does not mean data is processed in parallel afterwards. Processing still happens synchronously and thus one branch after another. Do not assume any specific order of the processing on the different branches after the split.   It is common to do a split and let only parts of the original data flow on through the branches. This effectively means a map is needed after a split. This map can be implicit or explicit.   Although FUs can have multiple input-pins it is preferrable in most cases to combine input data from different branches using an explicit join: The default output of a join is a tuple of its input values. The default behavior of a join is to output a value whenever a new input is received. However, to produce its first output a join needs an input for all its input-pins. Other join behaviors can be: reset all inputs after an output only produce output if data arrives on certain input-pins

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• How do I enable PHP apache_request_headers() or change PHP into an apache module

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  PHP, WHM, and several other services are already installed on a CentOS x64 server I am trying to migrate data to. Many of my existing PHP scripts are dependent on PHP's apache_request_headers() function, which the current server's PHP configuration does not support. Apparently, compiling PHP as an Apache module is one solution, but are there other ways to enable this (without uninstalling PHP, reinstalling, etc., and all dependent services), perhaps as easy as modifying php.ini, somehow?

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  - by George2

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