GNU pow( ) works only sometimes

[binladen]

anyone know why this works:

float y;

y = powf ( 2.0, 2.0 );


...and this does not (undefined reference to 'powf')?

float x, y, z;

x = 2.0;
z = 2.0;

y = powf ( x, z );

...can't be a library issue, as alluded to by the error msg, because using literals instead of variables works. The horror...

[dush]

Hi

I am using g++ and including <math.h>, everything works fine.
Have you tried pow instead of powf ?
pow is overloaded for float arguments too

#include <iostream>
#include <math.h>

using namespace std;

int main () {
	
float x, y, z;

x = 2.1;
z = 2.5;

cout << powf ( x, z ) << endl;
cout << pow ( x, z );

return 0;
}

output:

6.3907
6.3907

[pukur123]

Its library problem......

compile like this

gcc -lm program.c

Here lm option specifies that the C file contains some functions belonging to the libm library.

[binladen]

Thanks for the tips!
yeah, Im just wondering why it works with literals and not variables.

the -lm links in the math lib & variables work, sure.
And pow had the same hangup.

Its my first day using this compiler & I thought it a bit strange...

My code works..maybe I should just be happy:)