(group-by) ( groups elt key -- groups )

Vocabulary

grouping.extras.private

Inputs

groups	an object
elt	an object
key	an object

Outputs

groups

an object

Definition

USING: arrays kernel sequences vectors ;

IN: grouping.extras.private

: (group-by) ( groups elt key -- groups )
    pick [ t ] [ last first dupd = not ] if-empty
    [ swap 1vector 2array over push ]
    [ drop over last last push ] if ; inline