Re: lpeg.Carg() weirdness

[Parke <parke.nexus@...>]

On Sat, Jun 24, 2017 at 9:22 PM, Sean Conner <sean@conman.org> wrote:
>> Why?  What are you trying to do?
>
>   I have LPeg code to decode JSON data [1].  I received email from a person
> about the handling of 'null'---that is, I return a Lua nil value, but this
> person wanted a custom value.  I'm not completely swayed by the arguments
> for a custom JSON null value, but I would like to provide the option for
> such.  I thought a good way to handle a situation would be with Carg()---if
> you want a custom null value, one could be provided, but it's optional.

Why not use lpeg.Cc(values)?

Or possibly one of:
patt / number
patt / string
patt / function

http://www.inf.puc-rio.br/~roberto/lpeg/lpeg.html#captures

You would have to rebuild the pattern to change the value that would
represent null.

>   I'm just curious about the rational for the current behavior.

I find the current behavior to be consistent with other parts of Lua
that raise an error when the arguments provided to a function are
obviously wrong.

> -spc (Still pondering how to deal with this)

Use lpeg.Cc(values).  Or, if you don't want to rebuild the pattern,
use patt/function with a closure and with a monkey-patch a wrapper
around the match function to update the value in the closure.

-Parke