totient ( n -- t )

Vocabulary

math.primes.factors

Inputs

n	a positive integer

Outputs

t	an integer

Word description

Return the number of integers between 1 and n-1 that are relatively prime to n.

Definition

USING: combinators kernel math sequences ;

IN: math.primes.factors

: totient ( n -- t )
    {
        { [ dup 2 < ] [ drop 0 ] }
        [
            dup unique-factors
            [ 1 [ 1 - * ] reduce ] [ product ] bi / *
        ]
    } cond ; foldable flushable