mathematical power operator not working as expected

Question

short sho1, sho2;
printf("Enter two shorts.\n");
scanf("%hd %hd", &sho1, &sho2);
printf("%hd^%hd is %hd.\n", sho1, sho2, sho1^sho2);

When I enter '2 2', I get this output:

2^2 is 0.

How come? I'm using the MinGW GCC compiler in Eclipse, in case that's of any importance.

Just as a sidenote, if you simply want the square of an integer, don't use pow() but x*x. This saves you some floating point conversions. It seems obvious, but sometimes people tend to forget that. Including me when I looked the first time for a power operator :) — quinmars, Jan 08 '10 at 15:17

score 18 · Accepted Answer · answered Jan 08 '10 at 13:41

18

^ is not the mathematical power operator in C, it's the bitwise exclusive-OR operator. You probably want the pow function, which takes two doubles.

answered Jan 08 '10 at 13:41

ChrisInEdmonton

4,470
5
33
48

8

You can apply `^` to doubles, in which case the complier C truncates the values then exclusive ORs the bit patterns of the corresponding ints. When working on anti-collision algorithms for UAVs (uninhabited air vehicles), some sample code from NASA had an optimisation which never happened as it calculated squares using `dist^2`. (gcc 4 doesn't truncate; this was a few years ago on windows ) – Pete Kirkham Jan 08 '10 at 14:01
Oooh, +1 for very interesting comment. – ChrisInEdmonton Jan 08 '10 at 16:07

score 7 · Answer 2 · edited Jun 20 '20 at 09:12

7

You aren't using the operator that you think you're using.

^ is the bitwise XOR operator.

You are looking for the pow function.

Prototype: double pow(double b, double p);

Header File: math.h (C) or cmath (C++)

Explanation: This function raises b to the p power.

Wikipedia has a useful list of operators that are valid in C and C++.

edited Jun 20 '20 at 09:12

Community

1
1

answered Jan 08 '10 at 13:40

Bob Cross

22,116
12
58
95

use pow function from cmath/math.h – amit kumar Jan 08 '10 at 13:42
@Amit - yes, I was looking for a better formatted reference for the pow function. I'd forgotten about the cprogramming.com site. – Bob Cross Jan 08 '10 at 13:45

jason · Answer 3 · 2010-01-08T13:57:17.270

The ^ operator is not the power operator; it is the bitwise XOR operator. For the power operator you want to use the function pow declared in math.h. Thus:

pow(2.0, 2.0)

will return 4.0 (intentionally emphasizing that parameters and return value are doubles).

Note further that pow returns a double so you will have to change the format specifier to %g:

printf("%hd^%hd is %g.\n", sho1, sho2, pow((double)sho1, (double)sho2));

score 3 · Answer 4 · answered Jan 08 '10 at 13:43

3

There is no "power" operator in C - ^ is the XOR (bitwise exclusive OR) operator

answered Jan 08 '10 at 13:43

Sam Post

3,721
3
17
14

score 2 · Answer 5 · answered Jan 08 '10 at 13:43

2

You can use the pow() function in C.

pow(base, exponent);

It's in the math.h header file.

answered Jan 08 '10 at 13:43

Bill the Lizard

398,270
210
566
880

score 1 · Answer 6 · answered Jan 08 '10 at 13:42

1

In c ^, is the exclusive or operator. In order to do powers, you have to use the pow function.

pow(2,2)

answered Jan 08 '10 at 13:42

Brian Young

1,748
13
11

mathematical power operator not working as expected

6 Answers6

Linked