Rounding function not working

[harmonypig]

I can't figure out why the roundf function is not successfully rounding my numbers.

#include <stdio.h>
#include <math.h>

//function declarations

void CelToFah (int ctemp, int ftemp);
void FahToCel (int cel, int fah);
float roundf (float ftemp);
float roundf (float cel);

I use the roundf function in one of my other functions

void FahToCel (int fah, int cel)
{
//statements
printf("Please enter the temperature in Fahrenheit degrees.\n");
scanf("%d", &fah);
(cel=(((float)fah-32.0)*5.0/9.0));
roundf((float)cel);
printf("The temperature in degrees Celsius is %d.\n", cel);
return ;
//FahToCel
}

it produces a correct number when called, but it is not a rounded number, the roundf((float)cel) does nothing. I get the same number with and without it.

[SirPrattlepod]

roundf() returns something. You're never assigned that something that's returned to anything.

Also, you don't need all those casts.

[harmonypig]

void FahToCel (int fah, int cel)
{
//statements
printf("Please enter the temperature in Fahrenheit degrees.\n");
scanf("%d", &fah);
(cel=(((float)fah-32.0)*5.0/9.0));
cel=roundf((float)cel);
printf("The temperature in degrees Celsius is %d.\n", cel);
return ;
//FahToCel
}

is that what you mean by assign something? When I do that and try to run it I get an error saying "undefined reference to `roundf'"

[SirPrattlepod]

is that what you mean by assign something? When I do that and try to run it I get an error saying "undefined reference to `roundf'"

Yes that's what I meant.

You need to link with the math library. Usually add -lm to your compiler command line or in the makefile, but this may vary depending on which compiler you're using.

[harmonypig]

Thank you! That was definitely a step I was missing!
However, I still don't get a rounded number, for example if i enter 46 degrees C I get an output of 114, even though the real answer is 114.8 and it should round up to 115.

[SirPrattlepod]

The problem is that on line 6, you're assigning the result to cal (which is an int) so the truncation happens there. The floatf() function call is doing nothing.

Try deleting line 6 and replacing line 7 with

cel = roundf((fah-32.0)*5.0/9.0);

[harmonypig]

Thank you so much!