[erlang-questions] Parse Transform with Macros

Tristan Sloughter <>
Sun Mar 6 18:42:42 CET 2011


Hey, this is great! But the result it gives me fails when sent to erl_parse:

> {done,{ok,Tokens2,LineEnd2},StringRest2} = erl_scan:tokens([], "fun() ->
?MACHINE. ", 1).
{done,{ok,[{'fun',1},
           {'(',1},
           {')',1},
           {'->',1},
           {'?',1},
           {var,1,'MACHINE'},
           {dot,1}],
          1},
      []}
>  {ok, NewTokens2} = aleppo:process_tokens(Tokens2).

{ok,[{'fun',1},
     {'(',1},
     {')',1},
     {'->',1},
     {atom,1,'BEAM'},
     {dot,1},
     {eof,0}]}
> erl_parse:parse_form(NewTokens2).
{error,{1,erl_parse,["syntax error before: ","'fun'"]}}

Any ideas?

Thanks.

On Sun, Mar 6, 2011 at 11:27 AM, Evan Miller <> wrote:

> Hi Tristan,
>
> Aleppo will apply preprocessor macros on tokens returned by erl_scan:
>
> https://github.com/evanmiller/aleppo
>
> I think it will fit your needs. Aleppo also lets you use -ifdef and
> the like inside of functions since it uses a proper grammar for the
> macro syntax.
>
> On Sun, Mar 6, 2011 at 9:41 AM, Tristan Sloughter
> <> wrote:
> > I'd like to construct a parse transform that has a macro in the inserted
> > code. I've had no problem using erl_scan:tokens and erl_parse:parse_form
> to
> > construct the AST as long as no macros exist.
> >
> > Since macros are expanded before getting to this point it fails if in the
> > string scanned has something like ?MODULE. I looked at epp_dodger and
> > elsewhere but I can't seem to find something I could use to send in a
> string
> > like:
> >
> > "init() -> ?MODULE."
> >
> > And have tokens I could use to then generate the AST.
> >
> > Is this possible?
> >
> > Thanks,
> > Tristan
> >
>
>
>
> --
> Evan Miller
> http://www.evanmiller.org/
>


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