Hello PEG list, Suppose I have the following PEG:
S -> S S / a. For the string "aaaa", Warth et al.'s LR support method would yield the following tree: (a(a(a(aa)))). However, it has been suggested that the natural/expected tree for this string is really ((((aa)a)a)a). What does everyone think the parse tree should be for the following PEG: S -> S B / a B -> S I ask because supporting ((((aa)a)a)a) is, in effect, making a special case for left recursion in the presence of non-left recursion. But, if one were to think in terms of the language of B, then the parse of the above grammar should probably be (a(a(a(aa)))). If this is acceptable, then it means getting right-leaning trees with left recursion is no more complicated then adding an intermediary variable. The other side of things is that (roots of) left recursion should be prioritized over all else as a means of getting similar trees to what one might expect from a left-to-right bottom-up parser. What are people's thoughts on this? Best Regards, Peter Goodman, http://ioreader.com 70 Winston Circle, Montreal, Quebec H9S 4X6 _______________________________________________ PEG mailing list PEG@lists.csail.mit.edu https://lists.csail.mit.edu/mailman/listinfo/peg
