?set-once-at ( value key assoc -- value' first-time? )

Vocabulary

assocs.extras

Inputs

value	an object
key	an object
assoc	an object

Outputs

value'	an object
first-time?	an object

Definition

USING: assocs kernel ;

IN: assocs.extras

: ?set-once-at ( value key assoc -- value' first-time? )
    [ ?at not ] keep [ set-at ] curry [ keepd t ] curry
    [ nip f ] if ;