: keep ( A Variant -- B A )
    over
    swap
    call
    swap
;

: test-row-polymorphism ( -- )
    5 [ dup i.* ] keep
    5 test.assert-eq
    25 test.assert-eq

    "hello" [ string.length ] keep
    "hello" string.equal? test.assert
    5 test.assert-eq
;
