PetitParser Question

I’m following the example in the book (http://pharobooks.gforge.inria.fr/PharoByExampleTwo-Eng/latest/PetitParser.pdf, pp. 9-10) with a slight modification. I believe that the example evaluates things that have the same precedence from right-to-left (is that correct?). I’ve tried to adjust things so that it evaluates from left to right, but get an error. Any advice?

James

| number term prod prim start |

number := #digit asParser plus flatten ==> [ :str | str asNumber ].

term := PPDelegateParser new.

prod := PPDelegateParser new.

prim := PPDelegateParser new.

term setParser: (term memoized , $+ asParser trim , prod ==> [ :nodes | nodes first + nodes last ]) / prod.

prod setParser: (prim , $* asParser trim , prod ==> [ :nodes | nodes first * nodes last ]) / prim.

prim setParser: ($( asParser trim , term , $) asParser trim ==> [ :nodes | nodes second ]) / number.

start := term end.

start parse: '1 + 2'