Re: LPeg Matching Inverse of Set

[Mitchell <lists@...>]

Hi,

On Wed, 9 Mar 2022 15:17:39 +0000
Scott Morgan <blumf@blueyonder.co.uk> wrote:

> I'm starting out with LPeg but struggling with inverse matching on a set.
> 
> As an example, trying to match a substring without ';' or ',' chars
> 
>   patt = (-lpeg.S";,") ^ 1
> 
> Fails with "loop body may accept empty string"
> 
> Plain -lpeg.S";," does the right thing for the first char, so why
> doesn't ^ 1 extend that for longer strings?

Try this: (1 - lpeg.S";,")^1

It matches any one character minus those in the set, one or more times. A '-patt' by itself consumes no input, so it can match an empty string, and LPeg doesn't allow that for loops.

Cheers,
Mitchell