C/math.h/log2

log2: returns the base 2 logarithm for num

<source lang="cpp">

//Declaration: float log2f(float num);

              double log2(double num); 
              long double log2l(long double num);  

 #include <math.h>
 #include <stdio.h>
 int main(void)
 {
   double val = 1.0;
   do {
     printf("%f %f\n", val, log2(val));
     val++;
   } while (val<11.0);
   return 0;
 }
        

/* 1.000000 0.000000 2.000000 1.000000 3.000000 1.584963 4.000000 2.000000 5.000000 2.321928 6.000000 2.584963 7.000000 2.807355 8.000000 3.000000 9.000000 3.169925 10.000000 3.321928

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      </source>