#import std
#import nat
#import flo

lex = ~=' '*~F+ rlc both -=digits    # separate into tokens

parse = # build a tree

--<';'>; @iNX ~&l->rh ^/~&lt cases~&lhh\~&lhPNVrC {
   '*/': ^|C/~&hNV associate '*/',
   '+-': ^|C/~&hNV associate '*/+-',
   ');': @r ~&htitBPC+ associate '*/+-'}

associate "ops" = ~&tihdh2B-="ops"-> ~&thd2tth2hNCCVttt2C

traverse = *^ ~&v?\%ep ^H\~&vhthPX '+-*/'-$<plus,minus,times,div>@dh

evaluate = traverse+ parse+ lex