\ planckforth -
\ Copyright (C) 2021 nineties

defined? roll [unless]
    : roll ( wn ... w1 n -- w1 wn ... w2 -- )
        dup 0<= if drop else swap >r 1- recurse r> swap then
    ;
[then]


\ Ignore test codes. lib/tester.fs will redefine this when
\ running tests.
: T{
    begin
        word throw
        s" }T" streq if exit then
    again
;

s" Invalid argument" exception constant INVALID-ARGUMENT

: check-argument ( f  -- )
    unless INVALID-ARGUMENT throw then
;