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- Subject: Re: Matching sequences of identical characters with lpeg.
- From: Sean Conner <sean@...>
- Date: Tue, 20 Nov 2018 20:04:15 -0500
It was thus said that the Great Gabriel Bertilson once stated:
> Here's a solution using Cmt. As Andrew pointed out, Cb just inserts a
> capture into the list of captures returned by the current pattern, it
> doesn't match anything.
> Cg(1, "char") * Cmt(C(1) * Cb'char', function (_, _, char1, char2)
> return char1 == char2 end)^0
> It matches one character, labels it as "char", then matches further
> characters if they are equal to "char". To use it on "aaabbbcccd" in
> the Lua interpreter (with LPeg functions available as variables):
> > patt = Cg(1, "char") * Cmt(C(1) * Cb'char', function (_, _, cur, prev) return cur == prev end)^0
> > (C(patt)^1):match "aaabbbcccd"
> aa bbb ccc d
And it can be further extended to UTF-8:
local char = R"\1\127"
+ R"\194\244" * R"\128\191"^1
local seq = Cg(char,'char')
C(char) * Cb'char',
return cur == prev
local patt = C(seq)^1