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iOS Objective-C Basics (Retired) Functional Programming in C Functions

Posted by Justine Lam
Justine Lam
8,785 Points

The function example is pretty confusing

Okay, so I think I understand what's going on now. I think it's just confusing that he re-uses this function at the top and bottom:

int funky_math(int a, int b);

Doesn't seem very DRY to have that repeated at the bottom. I commented out the top portion and moved the bottom function up to the top: 

int funky_math(int a, int b) {
    return a + b + 343;

}

int main()
{
    int foo = 24;
    int bar = 35;
    printf("funky math %d\n", funky_math(foo, bar));

    return 0;
}
Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

can you post the code that is being used?

2 Answers

Justine Lam
Justine Lam
8,785 Points

This is what the code looked like originally: 

int funky_math(int a, int b);

int main()
{
    int foo = 24;
    int bar = 35;

    printf("funky math %d\n", funky_math(foo, bar));

    return 0;
}


int funky_math(int a, int b) {
    return a + b + 343;

}

So I need to have the initial function declared and then repeat it at the bottom with the actual math?

Andrew Shook
Andrew Shook
31,709 Points
Andrew Shook
Andrew Shook
31,709 Points

It depends on the compiler and version of the compiler you are using. I believe you can get away with declaring and defining all in one step with some, but your program may not run on all computers if you do that. However, if you want to maintain "best practices" then yes you need to declare it at the top and define it at the bottom.

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

if you dont want to include the function prototype (this line is the prototype: int funky_math(int a, int b); ) then you would have to define your function before using it like so:

int funky_math(int a, int b) {
    return a + b + 343;

}

int main()
{
    int foo = 24;
    int bar = 35;

    printf("funky math %d\n", funky_math(foo, bar));

    return 0;
}
Andrew Shook
Andrew Shook
31,709 Points
Andrew Shook
Andrew Shook
31,709 Points

Justine Lam, he isn't reusing the code he is declaring it. This has to do with the way a C compiler works. In order to set aside enough memory for a program the compiler needs to know what kinda of data it is working with. So all data must be declared( usually at the top of a file) before it can be defined. It has been a while since I programmed anything in C but I believe they changed this in the 2011 standards. Also, its kind of tradition in C to write a program that way.