Thread: functions to return 2 variables?

  1. #1

    Angry functions to return 2 variables?

    i'm trying to have a function return 2 values to 2 separate variables. i know the idea is for a function to only do 1 specific thing, and thats pretty much what my functions are doing. the only difference is, depending on user input, 1 of 2 different variables will be modified. SO, at the end of this function, i have it return 2 variables - 1 has been modified, 1 is the same as when the function began.

    i COULD go back and make 2 functions, which may be what i have to do, but it'd be really convenient if there was a way to be able to return multiple variables.

    this is what i have tried thus far - this is similar to the format in other programming languages (mainly math-oriented ones) so i thought it might work, but no luck:

    [int, int] functionname(variable1, variable2, variable3)

    then, in the main program, to call it, i put:

    [mainvariable1, mainvariable2]=functionname(variable1, variable2, variable3);

    and within the function i put:

    return(mainvariable1, mainvariable2);

    hoping that would do the trick to return 2 variables. it didn't.

    any help?

  2. #2
    Well, either you can return one value and write the other one through a pointer to a variable defined in main, write both through pointers, or return a pointer to an array of two variables defined in the function, or simply return a pointer.

    1) int function( int firstval, int *secondval )
    *secondval = ...;
    return firstval;


    variable = function( variable, &variable2 );
    printf( "%d %d", variable, variable2 );

    2) typedef int ( *ptr_to_ar )[2];
    ptr_to_ar function( int firstval, int secondval )
    static int intar[2];
    ptr_to_ar ptr = &intar;
    return ptr_to_ar;

    3) int *function( )
    int *ptr = malloc( x * sizeof( int ) );
    return ptr;

  3. #3
    Code Goddess Prelude's Avatar
    Join Date
    Sep 2001
    You can approach this several different ways, the pointer way:
    void function ( int *varOne, int *varTwo );
    /* The call */
    function ( foo, bar );
    The non-pointer return one way:
    int function ( int varOne, int VarTwo ) {
      if ( something for varOne ) {
        /* Set the value */
        return varOne;
      else if ( something for varTwo ) {
        /* Set the value */
        return varTwo;
        return /* error value goes here */
    Or you can just wrap both variables in a stuct and return that.

    There are many ways, but generally if you need to return two values your design is flawed and should be looked at.

    My best code is written with the delete key.

  4. #4
    In C a function can only return one variable, so you'll have to use duplicate functions or pointers.

  5. #5
    Join Date
    Aug 2001
    Groningen (NL)
    Another thing you could do is defining a structure which contains both values. Fill the structure in the function and return it. Or pass a structure to the function and let it be filled.

    You could also use an array, which can be filled or returned by the function.

  6. #6
    Shiro, I like your interesting solutions!

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