On Fri, May 13, 2011 at 9:48 AM, Dale Schumacher <dale.schumac...@gmail.com> wrote: > Parse tree production seems to be the issue at hand here, otherwise > all of the following are equivalent: > > expr = expr op expr | num > expr = expr op num | num > expr = num op expr | num > expr = num (op expr)*
Argh! Of course the grammar: expr = num (op expr)* should actually be: expr = num (op num)* We don't want both recursion and iteration at the same time! > num = [0-9]+:n $<#num, n> > expr = num:x ( '-' expr:y $<#diff, x, y>:x )* $x Similarly, this should be: expr = num:x ( '-' num:y $<#diff, x, y>:x )* $x to produce these results > Given "1" produces <#num, 1> > Given "1-2" produces <#diff, <#num, 1>, <#num, 2>> > Given "1-2-3" produces <#diff, <#diff, <num, 1>, <#num, 2>>, <#num, 3>> > which is left-associative. Hopefully, I haven't made any other silly errors. _______________________________________________ PEG mailing list PEG@lists.csail.mit.edu https://lists.csail.mit.edu/mailman/listinfo/peg
