lpeg-labels

A LPeg fork that intends to implement exception handling for error reporting, but for now just tracks the farthest failure position. More precisely, this fork changes lpeg.match to return nil plus a number when matching fails. This number is the farthest failure position that the PEG reached on the input string, and it is useful for adding error reporting while using LPeg to implement parsers.

Example

local lpeg = require "lpeg-labels"

print(lpeg.match(lpeg.P("a") * lpeg.P("a")^0, "ab")) -- 2, like the original LPeg
print(lpeg.match(lpeg.P("a") * lpeg.P("a")^0 * -lpeg.P(1), "ab")) -- nil    2, unlike the original LPeg