Talk about "build one to throw away"

FORLOOP.rx

## OBERON SYNTAX TO COMPILE:

  FOR x := start TO goal BY step DO
    block 
  END;

## StringTemplate ( generating retro code ):

  for_stmt(id, beg, end, step, block) ::= <<
  ( FOR ) <id>
  ( := ) <beg>
  ( TO ) <end>
  ( BY ) <step>
  ( DO 
  [
    <block>
  ]
  ( END ) FOR
  >>

## Retro helper macro

  ( -- for-loop compiler -------------------------------- )
  {{  ( helper functions )
  : relop ( n-q : given the step, pick correct comparison op )
    0 > [ ' <= ] [ ' >= ] if ;

  : lit,, ( n-  : pops number off stack and writes it as a literal )
    1 , , ;

  ---reveal--- 
  ( main routine )
  
  : FOR "( besq- ) compile a FOR loop, given begin, end, step, and (n-) quote" :doc
    immediate     ( COMPILE-TIME )
    push          ( besq- | -q )      ( RUN-TIME                            )
    rot           ( bes-esb )         ( ----------------------------------- )
    lit,,         ( esb-es )          (  -n  : n := begin )
    [ [[
      pop lit,,   ( es-es | q- )      ( n-nq : address of quote )
      ` sip                           ( nq-n : run block, preserve counter  )

                                      (      | a TO z BY +x | z TO a BY -x  )
                                      (      | -------------|-------------  )
      dup lit,, ` +                   ( n-n  :  n += step   |  n -= step    )
      ` dup relop lit,, ` do          ( n-nf :  n <= goal?  |  n >= goal?   )

    ]] ]
    ` while                           ( q- : loop until the quote returns 0 )
    ` drop                            ( n- : drop the loop var )
  ;
  }}


### Conclusion : NO THANK YOU!

The above code took several hours to write. 
It was educational, but what a complete mess! 
I'm not even going to try and run it.

What I should have done is implement simple IF and WHILE macros
first, and then build the FOR loop compiler out of those pieces.