stirling ( n k -- x )

Vocabulary

math.extras

Inputs

n	an integer
k	an integer

Outputs

x	an integer

Word description

Return the Stirling number of the second kind for a set with n elements partitioned into k disjoint non-empty sets.

Definition

USING: combinators.short-circuit kernel math.extras.private ;

IN: math.extras

MEMO: stirling ( n k -- x )
    2dup { [ = ] [ nip 1 = ] } 2|| [ 2drop 1 ] [ (stirling) ] if
    ;