Re: how to translate lua pattern "(.*)and(.*)" with lpeg re ?

[Albert Chan <albertmcchan@...>]

> On Feb 16, 2018, at 9:50 AM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> 
> 2018-02-16 16:09 GMT+02:00 albertmcchan <albertmcchan@yahoo.com>:
>> 
>>> On Feb 16, 2018, at 8:04 AM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
>>> 
>>> 2018-02-16 14:13 GMT+02:00 albertmcchan <albertmcchan@yahoo.com>:
>>>> I post this about a month ago.  I've found a simple lpeg re pattern for above
>>>> 
>>>> It can handle "repeated" separactor too, say, "(.*)andand(.*) too.
>>>> 
>>>> pat = re.compile( "{ (.(g <- &%z / .g))* } %z {.*}", { z = 'and' } )
>>>> 
>>>> note: the loop never match the first position, but it is ok
>>>> the second %z take care of of text with %z up front.
>>> 
>>> Just remind me ... since `lpeg` and `re` are packages you need
>>> to load into Lua, and standard Lua comes with a string library,
>>> why on earth would you want to do things in `re` that Lua can
>>> already do very well without it?
>> 
>> you are right.
>> 
>> If all I wanted were captures of "(.*)and(.*)", I would use string.match
>> I had picked the simple pattern to learn about lpeg matching.
>> 
>> But ... what if z = re.compile " 'and' %s+ ('possibly' / 'likely' / 'definitely') %s+ " ?
>> or, possibly even more complicated ?
>> 
>> Above lpeg re pattern can handle it
> 
> LPeg without `re` handles it too.
> 
>   C, P = lpeg.C, lpeg.P
>   kw = P'possibly' + 'likely' + 'definitely'
>   (C((1-kw)^0) * kw * (P(-1)/''+C(P(1)^0)))
> 

your lpeg pattern first capture is non-greedy.
it stop on the first kw match (also, P(-1) is unnecessary)

So, if kw = 'and', your lpeg is same as lua pattern "^(.-)and(.*)$"