Re: Profiling LPEG

[Sean Conner <sean@...>]

It was thus said that the Great Roberto Ierusalimschy once stated:
> >   Thanks for the confirmation.  I'm going to have to rethink my approach.
> 
> If that indeed is the culprit, you can still build a grammar in LPeg.
> You can build it piecemeal if you want:
> 
> + local G = {}
>   ...
> - local P = <some pattern>
> + G.P = <some pattern>
> + P = lpeg.V"P"
>   ...
> + G[1] = final_pattern
> + final_pattern = lpeg.P(G)

  I'm a bit unsure how to approach this though.  I'm looking at RFC-5322:
Internet Message Format.  It contains a bunch of rules that are used in
many other RFCs.  Just as an example, the RFC defines the following rules:

	quoted-pair	= ("\" (VCHAR / WSP))
	FWS		= ([*WSP CRLF] 1*WSP)	; folding text
	ctext		= ...		; ASCII minus ( ) \
	ccontent	= ctext / quoted-pair / comment
	comment		= "(" *([FWS] ccontent) [FWS] ")"
	CFWS		= (1*([FWS] comment) [FWS]) / FWS
	atext		= ... 		; ASCII plus some others
	atom		= [CFWS] 1*atext [CFWS]
	dot_atom_text	= 1*atext *("." 1*atext)
	dot_atom	= [CFWS] dot-atom-text [CFWS]
	qtext		= ...		; ASCII minus " \
	qcontent	= qtext / quoted-pair
	quoted_string	= [CFWS] DQUOTE *([FWS] qcontent) [FWS] DQUOTE
	word		= atom / quoted-string
	phrase		= 1*word
	unstructured	= (*([FWS] VCHAR) *WSP)

  RFC-7208 reuses 'dot-atom', 'quoted-string', 'comment', 'CFWS' and 'FWS'
(along with 'CRLF', 'ALPHA', 'DIGIT' and 'SP' from RFC-5234, and
'Local-part', 'Domain' and 'Mailbox' from RFC-5321).  RFC-5536 reuses 'FWS',
'comment', 'CFWS', 'atext', 'dot-atom-text' and 'phrase' (along with some
others not mentioned) from RFC-5322 (along with rules from RFC-2045,
RFC-3986, and RFC-5234).  Using LPEG grammars just doesn't work with that I
was trying to do.  At least, I don't think so.  

  -spc