Re: LPeg and function capture

[Philippe Lhoste <PhiLho@...>]

On 20/05/2012 16:11, Roberto Ierusalimschy wrote:
> > But the following doesn't, the function gets all chars, not only the
> > capital ones (those supposed to be captured):
> >
> > local patt = (findCap / function (a) return string.lower(a) end)^0
> > print(m.match(patt, toMatch))
> >
> > Why the behavior of the pattern is changed by the associated function?
>
> In all cases, the function is called once everytime there is a match.

Aah, that's something that totally escaped me when reading the 
description of the function capture.

> In the second case, there is match for each character (because of the
> (1 - cap) in 'findCap').

That's subtle!

> When the pattern of a function capture
> produces no captures, the entire match is given as the captured value.
>
> Maybe this is what you whant:
>
> local findCap = (1 - cap) + m.C(cap) / string.lower
>
> Now the function is called only when 'm.C(cap)' matches.

Ah, yes, the final pattern would then be:
local patt = ((1 - cap) + m.C(cap) / string.lower)^0

I understand the nuance now, thanks!

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Philippe Lhoste
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