Hello,
I just saw this mailing list, and figured if there's anywhere people
may know the answer to this question, it would be here.
I've been using the peg/leg parser generator tool to make C++ PEG
parsers (I modified it slightly so that it would generate C++ code
instead of ANSI C).
I'm trying to write a simple expression grammar using PEG and, like
everyone else I guess, have run into the left recursion issue. The
primary issue I have is the simplest kind, e.g.:
sum <- sum PLUS term
/ sum MINUS term
/ term
term <- term DIV value
/ term MUL value
/ term MOD value
/ value
value <- float-constant
/ int-constant
/ POPEN sum PCLOSE
note that I've written terminals in all caps above.
Now I can rewrite the grammar to eliminate the left-recursion, but
doesn't that change the associativity of the parse? That would be
quite bad since this grammar is primarily for mathematical
expressions...
So my question is: is anyone aware of an implementation (preferably in
C or C++) which could parse the above grammar? Even if it's not a
perfect tool, anything would be a better starting point for me than
having to implement one of the left-recursion PEG papers from scratch
:-)
cheers
Marcus
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