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

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Vocabulary
assocs

Inputs

key	an object
assoc	an assoc

Outputs

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

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

See also
at, at*, key?, of, ?of

Definition

USING: kernel ;

IN: assocs

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