Re: lpeg.Cb bug (?) with repeated evaluation of group capture pattern

[Sean Conner <sean@...>]

It was thus said that the Great Patrick Donnelly once stated:
> This is maybe relating to Sean Conner's recent post "Proposal for new
> LPeg function: lpeg.Ctab()".

  No, this doesn't have anything to do with my proposal (although I did try
using lpeg.Cb() before posting).

> I found that for some reason LPeg is evaluating a pattern in a group
> capture multiple times:
> 
> local patt = lpeg.Cg(lpeg.Ct"", "foo") * lpeg.Cb "foo" * lpeg.Cb "foo";
> print(patt:match "") --> table: 0x1634280        table: 0x16342c0
> 
> (two unique tables!) Or:
> 
> local patt = lpeg.P {
>     lpeg.Cg(lpeg.V "v", "foo") * lpeg.Cb "foo" * lpeg.Cb "foo";
>     v = lpeg.Ct "" / function(...) print(...) return ... end,
> }
> print(patt:match "") --> table: 0x233d4a0 \n table: 0x22f0ab0 \n
> table: 0x233d4a0        table: 0x22f0ab0
> 
> Whereas:
> 
> local patt = lpeg.Cg(lpeg.Cmt("", function(s,p) return p, {} end),
> "foo") * lpeg.Cb "foo" * lpeg.Cb "foo";
> print(patt:match "") --> table: 0x87a950 table: 0x87a950
> 
> (one table!)
> 
> Is this a bug?

  I don't know.  It certainly is surprising.  I wonder why it appears as if
lpeg.Ct() is being called each time lpeg.Cb() is called?

  -spc