coalesce ( alist -- specification )
Factor handbook » The language » Collections » Interval maps

Prev:

<interval-map> ( specification -- map )

Vocabulary
interval-maps

Inputs

alist

an association list with integer keys

Outputs

specification

array of the format used by <interval-map>

Word description
Finds ranges used in the given alist, coalescing them into a single range.

Definition

USING: arrays assocs kernel make math sequences sorting ;

IN: interval-maps

:: coalesce ( alist -- specification )
    [
        alist sort-keys unclip swap [ first2 dupd ] dip [|
        oldkey oldval key val |
            oldkey 1 + key = oldval val = and
            [ oldkey 2array oldval 2array , key ] unless key val
        ] assoc-each [ 2array ] bi@ ,
    ] { } make ;