BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  vector passed to function          BorlandTalk.com Forum Index -> C++ Builder (Language C++) View previous topic :: View next topic   Author Message DKat Guest Posted: Tue Nov 22, 2005 6:46 pm    Post subject: vector passed to function I have tried this several different ways and none of them will compile. void RandIndex(vector<short>, short) ; void RandIndex(&vector<short>, short) ; void RandIndex(std::vector<short>, short) ; and many others that were just plain wrong but I'm trying everything. I either get an link error (unresolved external) or a cannot convert x to y error. Help! please.... (and yes I did a search to find it this has been answered before). RandIndex(SoundIndex,NumberOfTrials); RandIndex(PictureIndex,NumberOfPictures); void RandIndex(vector<short> &ndx, short num) { randomize(); int x,temp,y; float f; for (x=0; x < num;++x) ndx[x] = x; for (x=0; x < num;++x) { f=rand(); f = f/32767; y = f * num; temp = ndx[y]; ndx[y] = ndx[x]; ndx[x] = temp; } } Back to top Chris Uzdavinis (TeamB) Guest Posted: Tue Nov 22, 2005 6:54 pm    Post subject: Re: vector passed to function "DKat" <disisdkatspam (AT) hotmail (DOT) com> writes: Quote: I have tried this several different ways and none of them will compile. It's very important that you show the exact error message(s) you received. At least the relevant ones. Otherwise it's hard to know what type of problem we're even trying to solve, unless it jumps out at us. Quote: void RandIndex(vector<short>, short) ; I'm assuming you're using the std namespace, or else this would fail to compile for not knowing what a vector is. Assuming that, this should compile, and will pass the argument by value (copying the vector.) Quote: void RandIndex(&vector<short>, short) ; This is invalid syntax. The ampersand should go after the type, not before it. Then it will pass the artument by reference. No copy involved. Quote: void RandIndex(std::vector<short>, short) ; This should compile, and will pass the argument by value (copying the vector.) Quote: and many others that were just plain wrong but I'm trying everything. I either get an link error (unresolved external) or a cannot convert x to y error. What are you WANTING it to do? Pass by reference or by value? An unresolved external occurs when you say there is a function that doesn't exist, and you call it. Quote: Help! please.... (and yes I did a search to find it this has been answered before). RandIndex(SoundIndex,NumberOfTrials); RandIndex(PictureIndex,NumberOfPictures); What are these two lines? Your invocations? What are the types of the arguments? It's also VERY important to show code that is complete enough that we can cut-and-paste it and get the same results you're asking about. Seeing out-of-context code is better than nothing, but it's not a good example. Right now I know you're calling RandIndex with something, and you're declaring the function somehow, but you're implementing it differently. Sorry that's not very useful. Quote: void RandIndex(vector<short> &ndx, short num) { .... } If that is your implementation, then your prototype should match it exactly. -- Chris (TeamB); Back to top DKat Guest Posted: Tue Nov 22, 2005 7:57 pm    Post subject: Re: vector passed to function I have never passed a vector to a function and what I have tried just doesn't work............... All I'm trying to do is have a function that can use arguments - one of which is a vector (it ise allocated before the function is called). The first argument is the array (vector<short>) and the second argument is the size of the array. The actually array itself must be changed so I do not want to pass by value (which shouldn't be happening with an array anyway?). I gave several different attempts that I had made at declaring the function. None of them work. I either get "[Linker Error] Unresloved external 'TMainForm::RandIndex(std::vector<short,std::allocator&, short)' reference from c:]......path..filename.obj Prototype = void RandIndex(vector<short> &, short); function = void RandIndex(vector<short> &ndx, short num){} Prototype = void RandIndex(vector<short>, short); Or [C++ Error] Control.cpp(315): E2034 Cannot convert 'vector<short,allocator' to 'vector<short,allocator *' [C++ Error] Control.cpp(315): E2340 Type mismatch in parameter 1 (wanted 'vector<short,allocator *', got 'vector<short,allocator') if I try to vary how I declare the prototype "Chris Uzdavinis (TeamB)" <chris (AT) uzdavinis (DOT) com> wrote Quote: "DKat" <disisdkatspam (AT) hotmail (DOT) com> writes: I have tried this several different ways and none of them will compile. It's very important that you show the exact error message(s) you received. At least the relevant ones. Otherwise it's hard to know what type of problem we're even trying to solve, unless it jumps out at us. void RandIndex(vector<short>, short) ; I'm assuming you're using the std namespace, or else this would fail to compile for not knowing what a vector is. Assuming that, this should compile, and will pass the argument by value (copying the vector.) void RandIndex(&vector<short>, short) ; This is invalid syntax. The ampersand should go after the type, not before it. Then it will pass the artument by reference. No copy involved. void RandIndex(std::vector<short>, short) ; This should compile, and will pass the argument by value (copying the vector.) and many others that were just plain wrong but I'm trying everything. I either get an link error (unresolved external) or a cannot convert x to y error. What are you WANTING it to do? Pass by reference or by value? An unresolved external occurs when you say there is a function that doesn't exist, and you call it. Help! please.... (and yes I did a search to find it this has been answered before). RandIndex(SoundIndex,NumberOfTrials); RandIndex(PictureIndex,NumberOfPictures); What are these two lines? Your invocations? What are the types of the arguments? It's also VERY important to show code that is complete enough that we can cut-and-paste it and get the same results you're asking about. Seeing out-of-context code is better than nothing, but it's not a good example. Right now I know you're calling RandIndex with something, and you're declaring the function somehow, but you're implementing it differently. Sorry that's not very useful. void RandIndex(vector<short> &ndx, short num) { ... } If that is your implementation, then your prototype should match it exactly. -- Chris (TeamB); Back to top DKat Guest Posted: Tue Nov 22, 2005 8:04 pm    Post subject: Re: vector passed to function Did I really proof read this???? sorryI have never passed a vector to a function and what I have tried just doesn't work............... All I'm trying to do is have a function that can use arguments - one of which is a vector (it is allocated before the function is called). The first argument is the array (vector<short>) and the second argument is the size of the array. The passed array itself needs to change so I do not want to pass by value (which shouldn't be happening with an array anyway?). I made several different attempts at declaring the function and prototype. None of them work. I either get "[Linker Error] Unresloved external 'TMainForm::RandIndex(std::vector<short,std::allocator&, short)' reference from c:]......path..filename.obj Prototype = void RandIndex(vector<short> &, short); function = void RandIndex(vector<short> &ndx, short num){} Or Prototype = void RandIndex(vector<short>, short); or the error [C++ Error] Control.cpp(315): E2034 Cannot convert 'vector<short,allocator' to 'vector<short,allocator *' [C++ Error] Control.cpp(315): E2340 Type mismatch in parameter 1 (wanted 'vector<short,allocator *', got 'vector<short,allocator') Prototype = void RandIndex(vector<short> *, short); function = void RandIndex(vector<short> *ndx, short num){} Back to top Dennis Jones Guest Posted: Tue Nov 22, 2005 8:23 pm    Post subject: Re: vector passed to function "DKat" <disisdkatspam (AT) hotmail (DOT) com> wrote Quote: Did I really proof read this???? sorryI have never passed a vector to a function and what I have tried just doesn't work............... All I'm trying to do is have a function that can use arguments - one of which is a vector (it is allocated before the function is called). The first argument is the array (vector<short>) and the second argument is the size of the array. The passed array itself needs to change so I do not want to pass by value (which shouldn't be happening with an array anyway?). I made several different attempts at declaring the function and prototype. None of them work. I either get "[Linker Error] Unresloved external 'TMainForm::RandIndex(std::vector<short,std::allocator&, short)' reference from c:]......path..filename.obj Prototype = void RandIndex(vector<short> &, short); function = void RandIndex(vector<short> &ndx, short num){} Or Prototype = void RandIndex(vector<short>, short); or the error [C++ Error] Control.cpp(315): E2034 Cannot convert 'vector<short,allocator' to 'vector<short,allocator *' [C++ Error] Control.cpp(315): E2340 Type mismatch in parameter 1 (wanted 'vector<short,allocator *', got 'vector<short,allocator ') Prototype = void RandIndex(vector function = void RandIndex(vector<short> *ndx, short num){} Honestly, I'm having a little trouble making sense of your examples, but here is an example that will work: #include <vector> short int RandIndex( std::vector<short> &TheVector ) { // return one of the values from in the vector: return TheVector[ 5 ]; } // example usage std::vector<short> MyVector; // put some data in the vector: for ( short int i=0; i<10; ++i ) { MyVector.push_back( i*2 ); } // example call short int temp = RandIndex( MyVector ); // would return the value 10 (5 * 2) - Dennis Back to top Old Wolf Guest Posted: Tue Nov 22, 2005 9:09 pm    Post subject: Re: vector passed to function Chris Uzdavinis (TeamB) wrote: Quote: "DKat" <disisdkatspam (AT) hotmail (DOT) com> writes: I either get "[Linker Error] Unresloved external 'TMainForm::RandIndex(std::vector<short,std::allocator&, short)' reference from c:]......path..filename.obj Prototype = void RandIndex(vector<short> &, short); function = void RandIndex(vector<short> &ndx, short num){} Yes, these match, and should "work". Perhaps he declared RandIndex inside a class, but then defined a free function RandIndex. That would cause the error message he pasted. To "DKat": can you copy and paste your exact program that isn't working? If your "Prototype" is inside TMainForm and your "function" is outside it, you have to refer to the function as "TMainForm::RandIndex", eg: // in header file class TMainForm { void foo( vector<short> &v ); } // in cpp file void TMainForm::foo( vector<short> &v ) {} Back to top Chris Uzdavinis (TeamB) Guest Posted: Tue Nov 22, 2005 9:16 pm    Post subject: Re: vector passed to function "DKat" <disisdkatspam (AT) hotmail (DOT) com> writes: Quote: I have never passed a vector to a function and what I have tried just doesn't work............... All I'm trying to do is have a function that can use arguments - one of which is a vector (it ise allocated before the function is called). The first argument is the array (vector<short>) and the second argument is the size of the array. The actually array itself must be changed so I do not want to pass by value (which shouldn't be happening with an array anyway?). A vector is not an array, though there is a lot of similarity at a conceptual level. A vector is just a class. If you pass it by value, you get a copy, period. An array cannot be passed by value because it implicitly is transformed into a pointer. Also, vectors inherently know how big they are, so you don't need to provide the size to a function that recieves the vector. Quote: I gave several different attempts that I had made at declaring the function. None of them work. I either get "[Linker Error] Unresloved external 'TMainForm::RandIndex(std::vector<short,std::allocator&, short)' reference from c:]......path..filename.obj This is a problem of your definition (not your declaration) not matching what you're calling. Quote: Prototype = void RandIndex(vector<short> &, short); function = void RandIndex(vector<short> &ndx, short num){} Yes, these match, and should "work". Quote: [C++ Error] Control.cpp(315): E2034 Cannot convert 'vector<short,allocator' to 'vector<short,allocator *' [C++ Error] Control.cpp(315): E2340 Type mismatch in parameter 1 (wanted 'vector<short,allocator *', got 'vector<short,allocator') It looks like the compiler is seeing a function that takes a POINTER to a vector, but you're passing a reference to one. [rest omitted] -- Chris (TeamB); Back to top Andrue Cope [TeamB] Guest Posted: Wed Nov 23, 2005 9:19 am    Post subject: Re: vector passed to function DKat wrote: Quote: I have never passed a vector to a function and what I have tried just doesn't work............... Rule number one working with the STL: use a typedef :) typedef std::vector<short> TVectorShort; void func( TVectorShort & Wibble ); It'll save on typing and improve readability. Actually I'd rarely just use 'TVectorShort' but would instead use 'TVectorRandomShorts' or something equally specific. Quote: void RandIndex(vector<short> &ndx, short num) { randomize(); int x,temp,y; float f; for (x=0; x < num;++x) ndx[x] = x; How do you know that 'ndx' has enough elements in it to perform this assignment? If the function is supposed to assume that the caller will have preinitialised it (nasty idea) then add some verification ie; void RandIndex(vector { if( ndx.size()!=num ) ..do something or else size the vector on entry: void RandIndex(vector<short> &ndx, short num) { ndx.resize( num ); -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top DKat Guest Posted: Fri Nov 25, 2005 6:39 pm    Post subject: Re: vector passed to function The error was (I am very embarrassed to say) void MainForm::RandIndex(vector<short> &ndx, short num) vs void RandIndex(vector<short> &ndx, short num) (oops! I just forgot since I program both in C and builder C++ and then compounded the error by trying to change how I was declaring the arguments which I had done properly to begin with.....) However, I was given a lot of helpful advice and taught things I need to know in any case so thank you all very much. 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