assoc-intersect ( assoc1 assoc2 -- intersection )
Factor handbook » The language » Collections » Associative mapping operations » Set-theoretic operations on assocs

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Vocabulary
assocs

Inputs

assoc1	an assoc
assoc2	an assoc

Outputs

intersection

a new assoc

Word description
Outputs an assoc consisting of all entries from assoc2 such that the key is also present in assoc1.

Notes
The values of the keys in assoc1 are disregarded, so this word is usually used for set-theoretic calculations where the assoc in question either has dummy sentinels as values, or the values equal the keys.

Definition

USING: kernel ;

IN: assocs

: assoc-intersect ( assoc1 assoc2 -- intersection )
    swap [ nip key? ] curry assoc-filter ;