Simple loop examples in Forth

Simple loop example using begin and again:

\ Loop until i = j
\ i must be higher than j
: loop ( i j -- )
    begin   \                                                   ( i j )
    .s cr   \ Dump the stack for debugging purpose              ( i j )
    2dup    \ Duplicate i and j, since = will eat them          ( i j i j )
    =       \ Compare i and j and put result at top of stack    ( i j result )
    if      \ Enter if-body if top of stack is 0                ( i j )
        2drop   \ If i == j, cleanup and exit                   ( )
        exit
    endif
    1+      \ Increase j with one                               ( i j+1 )
    again   \ Jump back to begin
    ;       \ End word def

Simple loop example using begin and again and execution token.

\ Loop until i = j
\ i must be higher than j
: loop ( i j -- )
    begin   \                                                   ( i j )
    .s cr   \ Dump the stack for debugging purpose              ( i j )
    2dup    \ Duplicate i and j, since = will eat them          ( i j i j )
    =       \ Compare i and j and put result at top of stack    ( i j result )
    if      \ Enter if-body if top of stack is 0                ( i j )
        2drop   \ If i == j, cleanup and exit                   ( )
        exit
    endif
    1+      \ Increase j with one                               ( i j+1 )
    again   \ Jump back to begin
    ;       \ End word def

Sources

http://www.figuk.plus.com/webforth/En/TutorlT.htm