: long-words-only ( Variant -- Variant )
    [ string.length 4 i.> ] list.filter
;

: test-filter ( -- )
    "cat dog elephant mouse" " " string.split long-words-only
    dup list.length 2 test.assert-eq
    dup 0 variant.field-at "elephant" string.equal? test.assert
    1 variant.field-at "mouse" string.equal? test.assert
;
