Re: Generating a pretty AST with LPeg

[Duncan Cross <duncan.cross@...>]

On Wed, Jan 29, 2014 at 10:41 AM, Matthias Kluwe <mkluwe@gmail.com> wrote:
>
>     {
>       'FCALL', { 'foo', 'bar', 'baz' },
>       'FCALL', { 'asdf', 'qwer' }
>     }
>

>
> For better readability and "type safety" I'd rather like it to be
>
>     {
>       'FCALL', { name = 'foo', args = { 'bar', 'baz' } },
>       'FCALL', { name = 'asdf', args = { 'qwer' } }
>     }
>

It looks like the feature you want is lpeg.Cg(patt, name) [1].

For your example, here is an alternative version of FCALL using Cg:

>    local WS    = lpeg.S' \n\t'^0
>    local NAME  = lpeg.C( lpeg.R'az'^1 )
>    local PLIST = WS * ( NAME * ( WS * ',' * WS * NAME )^0 )^-1

  local NAME_f = lpeg.Cg(NAME, 'name')
  local ARGS_f = lpeg.Cg(lpeg.Ct(PLIST), 'args')

  local FCALL = lpeg.Cc'FCALL'
                 * lpeg.Ct( WS * NAME_f * '(' * ARGS_f * WS * ')' )


[1] http://www.inf.puc-rio.br/~roberto/lpeg/#cap-g

-Duncan