?value-at ( value assoc -- key/value ? )
Factor handbook » The language » Collections » Associative mapping operations » Lookup and querying of assocs

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Vocabulary
assocs

Inputs

value	an object
assoc	an assoc

Outputs

key/value	the key associated to the value or the value if the value is not present in the assoc
?	a boolean indicating if the value was present

Word description
Looks up the key associated with a value. If the value was not present, an error can be thrown without extra stack shuffling. This word handles assocs that store f.

Definition

USING: kernel ;

IN: assocs

: ?value-at ( value assoc -- key/value ? )
    2dup value-at* [ 2nip t ] [ 2drop f ] if ; inline