Thread: Trouble with linking files

I'm trying to learn how to link two files together so that I can send a floating point number from one file to the other. I either get a compiler error or the value sent is simply 0, not the number I entered.

I just began learning about linking files, so this is probably a very easy fix. Please let me know what I'm doing wrong.

File 1:

Code:

#include<stdio.h>

int main(float num)
{
	values();
	printf("\n...So you like %lf.", num);
	
	return 0;
}

File 2:

Code:

#include<stdio.h>

float values()
{
	#include<stdio.h>

float values()
{
	float num;
	
	printf("\nWhat's your favorite decimal number?\n");
	scanf("%lf", &num);
	
}
	


Thanks.

	
}

And where's your return statement in values? And where do you assign the value that should be returned in main?

[Think about calling something from the math library, like say sqrt. If you say sqrt(foo), the value is returned but doesn't go anywhere. You need to put the answer somewhere, if you want to have it later on -- as in bar=sqrt(foo).]

The value that is returned to main is being assigned using scanf...isn't it?

Code:

scanf("%lf", &num);

The same exact code works with integer values, but not with char or float.

Please don't get frustrated with my questions. I know I'm not skilled at programming.

How about this...why is this not working properly? I can make it work if I make it a single file with two functions, but I can't make it work as two files.

File 1:

Code:

#include<stdio.h>

int main()
{
	float i;
	i = values(0.5,0.4);
	printf("Num is %f.\n", i);	

}

File 2:

Code:

#include<stdio.h>

float values(float a, float b)
{
	float n;
        n = a-b;

	return n;
}

The values a and b aren't being sent properly. I don't understand why. Can someone explain why instead of telling me that I'm stupid and don't understand functions...I already know that much.

Originally Posted by magda3227

Please don't get frustrated with my questions. I know I'm not skilled at programming.

How about this...why is this not working properly? I can make it work if I make it a single file with two functions, but I can't make it work as two files.

File 1:

Code:

#include<stdio.h>

int main()
{
	float i;
	i = values(0.5,0.4);
	printf("Num is %f.\n", i);	

}

File 2:

Code:

#include<stdio.h>

float values(float a, float b)
{
	float n;
        n = a-b;

	return n;
}

The values a and b aren't being sent properly. I don't understand why. Can someone explain why instead of telling me that I'm stupid and don't understand functions...I already know that much.

How do you know? Do you not get 0.1 (or the nearest float equivalent)? What error/other output are you getting?

Originally Posted by tabstop

How do you know? Do you not get 0.1 (or the nearest float equivalent)? What error/other output are you getting?

I used

Code:

printf("%f", a);

in the second file to check if a was sent properly, but it output 0.

The overall output of the program is something large negative number like -17332847.

So, if you're not using prototypes (i.e., if what you've typed is actually what you've got) then you're getting loads of warnings about that. You need to tell main that the function values exists (normally you would put the prototype in a header file, like values.h, which you can then #include), otherwise the floats will get passed as ints (the default "I don't know what it is" variable type in C).

Thanks. Using the prototypes worked.

I hate to ask another question, but how would you have a function return an array so that it can be stored into a different array in the main function? For example...

file2 creates an array A that is m integers long. How would I return A[m] to the main function and store it as an array B[m] in which I can access each member of the array? Basically, I want to copy the array from one file to the other. How would this be done?

I don't understand much about pointers, but have a feeling that they would be used here. If so, does anyone know any good resources for learning more about pointers? Every one I find is confusing. The more examples, the better for me. I learn visually.
Thank you for all the help.

You can't return arrays.

You can return pointers to memory, so you would have to grab some memory with malloc (you can "pretend" it's an array, for example, by using foo[i] notation) and pass it around.

However, the general method is to pass the array in and out as an argument, rather than returning it.