log2 ( x -- n )
Factor handbook » The language » Numbers » Mathematical functions » Integer functions

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Vocabulary
math

Inputs

x	a positive integer

Outputs

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