CODEWITHSUNDEEP
cpow
Tomaso
Tomaso

Reputation: 15

pow value is wrong without a dot

I have this program that makes a geometric mean, I know it can be done with cbrt instead of pow, but my question is the next

//medida geometrica de 3 numeros

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

int main(){

    double n1, n2, n3, mult, media;

    printf("introduce los 3 numeros espaciados con un espacio cada uno:");
        scanf("%lf %lf %lf", &n1, &n2, &n3);

    mult = n1 * n2 * n3;
    media = pow(mult, 1/3.);


    printf("\nLa media geometrica es de:%lf", media);

}

The question is why pow gives me a wrong value if I don't write a dot after the 3 in the pow function pow(mult, 1/3.)

I mean if i write pow(mult, 1/3) without the dot after the 3 it gives me a wrong value and I don't know why

Thanks in advance.

Upvotes: 1

Views: 57

Answers (2)

Fiddling Bits
Fiddling Bits

Reputation: 8871

There is a big difference in the result of 1/3 and 1/3..

The first uses integer division. The quotient is 0 and the remainder is 1, which is thrown out (or truncated), resulting in final value of 0.

The second uses floating point division which results in the expected value, (approximately) 0.333....

Upvotes: 2

dbush
dbush

Reputation: 225827

When you do 1/3, both arguments have integer type so the result is also an integer and you get 0.

When you do 1/3., one argument has type double so the other is converted to that type and floating point division is done, so you end up with the expected value.

Upvotes: 2

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