count= ( ... seq quot: ( ... elt -- ... ? ) n -- ... ? )

Vocabulary

sequences.extras

Inputs

seq	a sequence
quot	a quotation
n	an integer

Outputs

?

a boolean

Word description

Returns t if the sequence has exactly n elements where quot returns true, otherwise returns f.

Definition

USING: kernel math sequences ;

IN: sequences.extras

: count= ( ... seq quot: ( ... elt -- ... ? ) n -- ... ? )
    [ 0 ] 3dip
    [ '[ swap _ dip swap [ 1 + ] when dup _ > ] find 2drop ]
    keep = ; inline