fold ( ... obj branches -- ... value )

Vocabulary

bend

Inputs

obj	an object
branches	a sequence of type/quotation pairs, with an optional quotation at the end

Outputs

value

The result of the fold

Word description

Unpacks the slots of a tuple, recursively calling fold on slots with a type matching the original object (Except for slots typed with object). Then calls the branch according to object type, to produce a value.

Definition

USING: accessors classes classes.algebra classes.tuple
combinators kernel quotations sequences ;

IN: bend

: fold ( ... obj branches -- ... value )
    [
        [ dup callable? [ first dupd instance? ] unless ] find
        nip first2 pick
    ] keep [ fold ] curry [
        [ [ class>> ] ] dip
        [ class-of swap [ class<= ] [ object = not ] bi and ]
        curry compose
    ] dip [ when ] curry compose [
        [
            [ tuple-class? [ tuple-slots ] [ drop f ] if ]
            [ nip all-slots ] 2bi
        ]
    ] dip [ [ ] 2map-as ] curry compose dip compose
    ( ... -- ... value ) call-effect ; inline recursive