gforth-tutorial/15-breaking-returning.fth

\ Looping is fine, but what, if one needs to break a loop?

: mydef
  10 5 u+do
  i 2 mod 0 =
  if
    ." at index: " i . cr
    ." hit an even number -- oh noes!" cr
    \ Need to call `unloop` to not mess up everything. Loops
    \ have implicit variables on the stack, to represent
    \ their state. These variables need to be cleaned up
    \ before exiting.
    unloop
    \ exit leaves the current definition. So it is like
    \ `return` in other languages.
    exit
  then
  loop ;

: mydef
  10 5 u+do
  i 2 mod 0 =
  if
    ." at index: " i . cr
    ." hit an even number -- oh noes!" cr
    \ `leave` seems to do both, `unloop` and `exit`. It is a
    \ cleaner way of doing things, because there is no way
    \ to forget to unloop.
    leave
  then
  loop ;