Vocabulary
math

Inputs and outputs

x	a positive integer
n	an integer

Word description
Outputs the largest integer n such that 2^n is less than or equal to x.

Errors
Throws an error if x is zero or negative.

Definition

USING: kernel math.private ;

IN: math

: log2 ( x -- n )
dup 0 <= [ log2-expects-positive ] [ (log2) ] if ; inline