C power function and scanf

Question

So basically, I need to get an input and square it. some reason the pow() function isn't working.

#include <stdio.h>
#include <math.h>
int main (){

  int in, ans;
  scans("%d", &in);
  ans = pow(in, 2);
  printf("answer is: %d", ans);
  return 0;

}

The error is :

undefined pow or something like that

answer is , 'show exact error message' , or something like that — pm100, Mar 27 '17 at 17:11
Assuming a linker error? Hard to say when we don't have an exact error message. Could always do `in * in` to square it too. — Michael Dorgan, Mar 27 '17 at 17:13
I strongly suggest squaring the input by multiplying it by itself, especially since it is an integer, and the answer is (apparently) expected to fit in an integer. `ans = in * in;` — John Bollinger, Mar 27 '17 at 17:15
Carefully reproducing error message is a **key prerequisite** to getting good answers. You wouldn't be satisfied with an answer like "there must be a library missing or something like that" would you? — fvu, Mar 27 '17 at 17:16
Possible duplicate of [Why do you have to link the math library in C?](http://stackoverflow.com/questions/1033898/why-do-you-have-to-link-the-math-library-in-c) — ad absurdum, Mar 27 '17 at 17:50

Ankur Jyoti Phukan · Answer 1 · 2017-03-27T17:25:36.277

2

This type of error occur when you forgot to link your programme to the math library .
use -lm for linking to math library.

gcc yourfilename.c -lm

to use the math library

edited Mar 27 '17 at 17:25

answered Mar 27 '17 at 17:10

Ankur Jyoti Phukan

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score 0 · Answer 2 · answered Mar 27 '17 at 17:15

0

I think you have compiled on Linux platform. So, use -lm option with command.

gcc yourfile.c -lm

answered Mar 27 '17 at 17:15

msc

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score 0 · Answer 3 · answered Mar 27 '17 at 17:21

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You are using scans instead of scanf. It should scanf("%d",&in);

answered Mar 27 '17 at 17:21

Mohit Yadav

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Right..but that's probably a typo.... – Sourav Ghosh Mar 27 '17 at 17:24

C power function and scanf

3 Answers3