Passing Value back problem

My program asks the user to input sold and price. both are floting point number. they use the same function for validation. the function checks the input data which must be 0-9 and/or "."
i use "pass" for checking true or false. it is supposed to send the value of "pass" to the main but it isn't
how can i fix this problem?
Thanks

Code:

#include <stdio.h>
#include<string.h>
#include<stdlib.h>

void check(struct Sell s,char amoun[50]);
struct Sell 
{
	float amountsold,retailprice;
	bool pass;
};
//******************M a i n*************
	
 int main  (void)

{
struct Sell st;
bool k=true;
char amountsol[50],retailprice[50];
int e,len,i;
st.pass=true;
	do
	{
			
			
		do
		{
		    puts("Enter  amount sold: ");
		    gets(amountsol);
		    check(st,amountsol);
		    printf("Pass Main:%d\n",st.pass);
		}while(!st.pass);
	 st.amountsold=atof(amountsol);
	printf("Amoundsold :%f\n",st.amountsold);
		do
		{
		puts("Enter retailprice: ");
		gets(retailprice);
		check(st,retailprice);
		printf("Pass Main :%d\n",st.pass);
		}while(!st.pass);
	st.retailprice=atof(retailprice);
	} while(!st.pass);
	
	printf("Amountsold :%f \n",st.amountsold);
	printf("amountinFunct: %f\n",st.retailprice);
}
//**********f u n c t i o n ********************
void check(struct Sell s,char num[50])
{
			
int e,len,i,n;
len=strlen(num);
for (e=0;e<len;e++)
         {
	switch (num[e])
              {
					
	case '0' : 
                 	case '1' :
                 	case '2' :
                  	case '3' :
                  	case '4' :
                  	case '5' :
                    case '6' :
                  	case '7' :
                  	case '8' :
                  	case '9' :
                  	case '.' :
                  	s.pass=true;
                  	printf("Pass Funct:%d\n",s.pass);
                  	break;
                  	default : 
                    s.pass=false;
                    printf("Pass Funct:%d\n",s.pass);
                    puts(" Amount sold error \n");
           	break;
           	}
           }
    
           printf("Pass in Function before return :%d\n",s.pass);
return(s.pass);
}

if im not wrong, which i could well be, the problem is in your function declaration.

void function(params)

that means it wont pass anything back. wat u want is probably this:

bool function(params)

which indicates itll return a bool, or int as main does "int main(), etc.

im relatively new to c but i think this is right P

it doesn't seem to be working
any suggestion?
cheers

another thing u might try
since Check returns s.pass...it wont modify s.pass in the function that calls it.
this will:
s.pass = check....

as s.pass becomes the returned value

or

if(check(...))

etc.

Originally posted by Unregistered
it doesn't seem to be working
any suggestion?
cheers

Did you remember to change both the prototype and the function return specs:

>bool check(struct Sell s, char amoun[50]);

Hammer
i tried it but nothing change :-(

Here's the output I get from you prog after making a few changes. Can you go through this and verify it:

Enter amount sold:
10
Pass Funct:1
Pass Funct:1
Pass in Function before return :1
Pass Main:1
Amoundsold :10.000000
Enter retailprice:
100
Pass Funct:1
Pass Funct:1
Pass Funct:1
Pass in Function before return :1
Pass Main :1
Amountsold :10.000000
amountinFunct: 100.000000

If it's correct, all I did was

- Change return type on function check() from void to bool.
- Moved the structure definition to before the function check()'s prototype. This is because you were using it before defining it.
- I also had to typedef an int to bool, and using #define's for true/false as my compiler doesn't recognise them.

Let me know how you get on.

Thanks Hammer
just woke up
i am quite new with C
i did what u told me except the last one
"- I also had to typedef an int to bool, and using #define's for true/false as my compiler doesn't recognise them. "
i don't know how to do it
the point of this program is when u put any character in to the number, for example 12.a ,2w,s, 150.y etc,it should show an error message and ask the same question for u to put the number again
thanks

OK, I see your next problem (where I come from they're called challenges, not problems!).

The struct within main() is passed to the function check(). This function then has it's own copy of the struct to play with, and alter as it sees fit. Any changes made to the struct within check() do not affect the struct in main() simply because they are 2 seperate variables.

Also, you return a value from check(), but you never assign it to anything in main(). I think a better example of using check() would be like this

Code:

st.pass = check(amountsol);
if (st.pass)
/* etc etc */

You don't have to do it that way, it's up to you. Whatever you do though will require a few tweaks in your code. Have another try and post here again when you're ready.

You could always do:

Code:

struct mystruct myfunction( struct mystruct x )
{
    struct mystruct y;
    y = x;
    ... do stuff to y ...
    return y;
}

Then call it:

struct mystruct someVar;

someVar = myfunction( someVar );

There's a way of changing a value without passing it as a pointer. Basicly pass it by value, and then modify the original with the return-by-value.

Quzah.

thanks you guys
i solve this problem
actually it was my mistake i was just confused
Thanks