Thread: reference parameters

Due to the lack of reference parameters being available in C, i need to use pointers to change a value with a function, but I can't seem to figure out how I can pass an array to a function and change the array values, is there a thread somewhere which covers this? or can someone give me an example? thnx

EDIT: I believe I figured it out, someone correct me if I'm wrong plz

example:

Code:

#define elements 4

int somearray[elements];

void arraychanging(int* array[],int elements)
{
int counter = 0;

  for(counter = 0;counter<elements;counter++){
    *array[counter] = 1
  }
}

arraychanging(&somearray,elements);

pointers in C are nearly identical to references in C++. There are only a couple minor differences

1. The function that passes the argument: There is no difference in how to pass an array -- both C and C++ are identical. Passing a single object: C needs the & operator, while c++ does not

Code:

//
// *.c file
//
struct mystruct
{
    int a;
    int b;
};

void foo(int array[], int* b, struct mystruct* c)
{
   c->a = 0;
   *b = 0;
}

int main()
{
    int array[5];
    int b;
    struct mystruct c;

   foo(array, & b, &c);
}

Code:

//
// *.cpp
//
struct mystruct
{
    int a;
    int b;
};

void foo(int array[], int& b, mystruct& c)
{
   c.a = 0;
   b = 0;
}


int main()
{
    int array[5];
    int b;
    mystruct c;
   foo(array,  b, c);
}

Code:

void arraychanging(int array[], int size)
{
   int i = 0;
   for ( i = 0; i < size; ++i )
   {
      array[i] = 1;
   }
}

int main(void)
{
   int somearray[4];
   arraychanging(somearray, 4);
   return 0;
}

Originally Posted by LowLife

but this will not change the array values in my main function, it will just change them within the function arraychanging, I want the array that I pass to be altered, like a reference parameter in c++, thus meaning I have to use pointers

Have you tried it? What Dave_Sinkula posted should work. They contents of the array passed into the function should remain modified after exiting said function.

BTW: This wouldn't work.

Code:

#define elements 4

void arraychanging(int* array[],int elements)

The preprocessor would turn that into this:

Code:

void arraychanging(int* array[],int 4)

...prior to compiling which would of course give you an error. That's why defines are typically made all caps to differentiate them from normal variables:

Code:

#define ELEMENTS  4

You don't normally "include" source code from one source file in another file. You would "include" a header containing a function prototype perhaps. That said, it shouldn't matter where the function's code is located. You could also try this:

Code:

void arraychanging(int * array, int size)
{
    int i = 0;
    for ( i = 0; i < size; ++i )
    {
        array[i] = 1;
    }
}

Which is the same thing Dave posted except with a * instead of a [] in the function parameter list. That should also work.

Why don't you try posting a complete (compilable) but minimal program example that you are trying to get working but that still demonstrates this behavior you are seeing. Make sure to delineate which code is in which source file.

Hmm, sorry Dave_Sinkula, what you said was true, there seemed to be something wrong with my including files

hk_mp5kpdw, I am using seperate source and header files, the source file are my functions, and the header file are my functions prototypes, so no problems there

giving you my source wouldn't really help you, I'm programming in C, yes, but the app I'm creating is build for the PSP...

anyway, I figured it out, thnx all for the help