intern ( obj hash-set -- obj' )

Vocabulary

hash-sets

Inputs

obj	an object
hash-set	a hash-set

Outputs

obj'	a previously retained or the original object

Word description

If a value equal to obj is present in the hash-set, return the copy from the set, otherwise add obj to the hash-set and return the original. When used with strings, this word can be used to implement string interning, see https://en.wikipedia.org/wiki/String_interning.

Side effects

Modifies hash-set

See also

cache

Definition

USING: hash-sets.private kernel sequences sets ;

IN: hash-sets

: intern ( obj hash-set -- obj' )
    2dup key@ [ swap nth 2nip ] [ 2drop [ adjoin ] keepd ] if ;