Can anyone tell me what ive done wrong and breakdown how to properly prototype and deploy created functions?

Question

code:

#include <stdio.h>
#include <cs50.h>
#include <string.h>
#include <ctype.h>
#include <math.h>

// PROTOTYPE THE FUNCTONS & DECLARE VARIABLES

int multiply(int ,int);

void get_input(int , int);

    int input1;
    int input2;
    int answer;

// RUN THE MAIN PROGRAMME

int main(void)

{

        // EXECUTE GET_INPUT FUNCTION

        get_input(input1, input2);

        // EXECUTE MULTIPLY FUNCTION

        multiply(input1, input2);

}


    // DEFINE GET_INPUT FUNCTION

    void get_input(input1, input2)
    {

        printf("give me 2 integers\n");

        do
        {

        input1 = get_int("Integer 1: ");
        input2 = get_int("Integer 2: ");

        }

        while ((input1 || input2) <= 0);

    }

    // DEFINE THE MULTIPLY FUNCTION

    answer multiply(input1, input2)

    {

        int answer = (input1 * input2);

        printf("%i", answer);

    }

errors:

~/Week_2/Practice/ $ make functionpractice
clang -ggdb3 -O0 -std=c11 -Wall -Werror -Wextra -Wno-sign-compare -Wno-unused-parameter -Wno-unused-variable -Wshadow    functionpractice.c  -lcrypt -lcs50 -lm -o functionpractice
functionpractice.c:36:20: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
    void get_input(input1, input2)
                   ^
functionpractice.c:13:9: note: previous declaration is here
    int input1;
        ^
functionpractice.c:36:28: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
    void get_input(input1, input2)
                           ^
functionpractice.c:14:9: note: previous declaration is here
    int input2;
        ^
functionpractice.c:55:5: error: unknown type name 'answer'
    answer multiply(input1, input2)
    ^
functionpractice.c:55:21: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
    answer multiply(input1, input2)
                    ^
functionpractice.c:13:9: note: previous declaration is here
    int input1;
        ^
functionpractice.c:55:29: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
    answer multiply(input1, input2)
                            ^
functionpractice.c:14:9: note: previous declaration is here
    int input2;
        ^
functionpractice.c:59:13: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
        int answer = (input1 * input2);
            ^
functionpractice.c:15:9: note: previous declaration is here
    int answer;
        ^
6 errors generated.
<builtin>: recipe for target 'functionpractice' failed
make: *** [functionpractice] Error 1

Answer 1

#include <stdio.h>
#include <cs50.h>
#include <string.h>
#include <ctype.h>
#include <math.h>

// PROTOTYPE THE FUNCTONS

int get_input();

int multiply(int input1, int input2);

// RUN THE MAIN PROGRAMME

int main(void)  {

            //DECLARE THE VARIABLES WITHIN THE MAIN PROGRAMME FUNCTION FOR USE IN OTHER FUNCTIONS WITHIN MAIN

            int input1;
            int input2;

            printf("give me 2 positive integers\n");

                do {

                    input1 = get_int("Integer 1: ");
                    input2 = get_int("Integer 2: ");

                    }

            while ((input1 || input2) <= 0);

            // EXECUTE MULTIPLY FUNCTION

            multiply(input1, input2);

            int result = multiply(input1, input2);

            printf("the answer to %i x %i = %i\n", input1, input2, result);

            }











// DEFINE THE MULTIPLY FUNCTION

int multiply(int input1, int input2)

{

    int answer = (input1 * input2);

    return answer;

}

Got there in the end.

basically i was trying to do too much via functions and left essentialy nothing in "main". its not possible to globally declare my variables and call them into use in functions outside of main.

Main things I need to remember:

• The compiler strictly reads from top to bottom in regards to user inputs and variables.

• Function outputs are best reassigned within main for further use.

Answer 2

You need define a name for arguments and not just data types.

In the function prototype, you will declare it like this:

int multiply(int input1, int input2);

For the function definition, you copy the function prototype remove the semicolon and add curly braces like this:

int multiply(int input1, int input2)
{
    //Code here
}