Trouble with powers in C?

Question

Trying to find the 2^5 and 2^-5 using C. This is what I've got but the output for 2^-5 is coming up as 0.00000 and I'm not sure why. I can't use any math libraries, so that's out.

int main(void)
{
	int x, n, k;
	int answerpositive;
	float answernegative;

	x=2;
	n=5;
	answerpositive = 1;

	for (k=0; k<n; k++)
	{
		answerpositive = answerpositive*x;

	}

	printf("%d       ", answerpositive);

	answernegative = 1/answerpositive;

	printf("%f", answernegative);

	return EXIT_SUCCESS;

}

peteams · Accepted Answer

Change

answernegative = 1 / answerpositive;

to

answernegative = 1.0 / answerpositive;

or

answernegative = 1 / (float)answerpositive;

Your original division has ints on both sides, to integer division takes place before being implicitly cast to a float. If you change one side of the division to a float (e.g. by using 1.0 rather than 1) then floating point division will occur and all will be well!

ʄaçade · Answer

answerpositive is declared as integer.

So any division as

1/answerpositive;

is going to be zero.  An integer divide.  Instead, declare your answers as float  or double.  Do not use one for positive and another for negative.

Trending News

Trouble with powers in C?

2 Answers