Retro's arithmetic functions are based on those in [[Forth]]. The example is an adaption of the one from Forth.
 
:arithmetic (ab-)
  over       '\na_______=_%n s:put
  dup        '\nb_______=_%n s:put
  dup-pair + '\na_+_b___=_%n s:put
  dup-pair - '\na_-_b___=_%n s:put
  dup-pair * '\na_*_b___=_%n s:put
  /mod       '\na_/_b___=_%n s:put
             '\na_mod_b_=_%n\n" s:put ;