log2 not found in my math.h?

Question

I\'m using a fairly new install of Visual C++ 2008 Express.

I\'m trying to compile a program that uses the log2 function, which was found by including using Eclipse

Answer 1

If you're trying to find the log2 of strictly integers, some bitwise can't hurt:

#include 

unsigned int log2( unsigned int x )
{
  unsigned int ans = 0 ;
  while( x>>=1 ) ans++;
  return ans ;
}

int main()
{
  // log(7) = 2 here, log(8)=3.
  //for( int i = 0 ; i < 32 ; i++ )
  //  printf( "log_2( %d ) = %d\n", i, log2( i ) ) ;

  for( unsigned int i = 1 ; i <= (1<<30) ; i <<= 1 )
    printf( "log_2( %d ) = %d\n", i, log2( i ) ) ;
}