Function to add double values in C

Question

I wrote a function to add two double values:

# include <stdio.h>

double addem(double input1, double input2)
{
    double sum ;
    sum = input1 + input2 ;
    return input1 + input2 ;
}

int main(){
    double in1,in2, add = 0 ;
    printf("Enter the numbers\n");
    scanf("%f", &in1);
    scanf("%f", &in2);
    /* Calling function */
    add = addem(in1, in2);
    printf("Sum = %f\n", add);
    
    return 0;
}

However the result always returns a zero:

Enter the numbers
3
3
Sum = 0.000000

Aside: Don't declare more variables than required. Simply `return input1 + input2`. — Harith, Apr 25 '23 at 16:01
A decent compiler should be complaining, and if yours doesn't then enable more warnings. Treat warnings as errors. Mismatching format specifier and argument type leads to *undefined behavior*. — Some programmer dude, Apr 25 '23 at 16:02
Does this answer your question? [Why does scanf() need "%lf" for doubles, when printf() is okay with just "%f"?](https://stackoverflow.com/questions/210590/why-does-scanf-need-lf-for-doubles-when-printf-is-okay-with-just-f) — Raymond Chen, Apr 25 '23 at 16:03
And *always* check what `scanf` [*returns*](https://en.cppreference.com/w/c/io/fscanf#Return_value). — Some programmer dude, Apr 25 '23 at 16:03

score 1 · Accepted Answer · answered Apr 25 '23 at 15:59

1

Save time and enable all warnings.

double in1,in2, add = 0 ;
....
scanf("%f", &in1);  // Use %lf with double *

answered Apr 25 '23 at 15:59

chux - Reinstate Monica

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It works. Had known about `lf` but didn't realize. Thanks a lot! – kartiks77 Apr 25 '23 at 16:01
1

@kartiks77 What compiler are you using? Did you enable all warnings or just re-write the format? If you did not enable more warnings, the real mistake still exists. – chux - Reinstate Monica Apr 25 '23 at 16:02

Function to add double values in C

1 Answers1