[Caml-list] possible camlp4 problem/bug with literal booleans in expr quotations.

[Caml-list] possible camlp4 problem/bug with literal booleans in expr quotations.

[Maas-Maarten Zeeman]

Hi,

I'm experimenting with camlp4 and found this problem.

file: forever.ml

   #load "q_MLast.cmo";;
   #load "pa_extend.cmo";;

   open Pcaml;;

   EXTEND
     expr: LEVEL "expr1"
       [ [ "forever"; body=expr ->
              <:expr< while true do { $body$ } >> ] ];
   END;;

file: bar.ml

   let _ = forever print_string "0";

compilation:

   $ ocamlc -pp camlp4o -I +camlp4 -c forever.ml
   $ ocamlc -pp "camlp4o ./forever.cmo" bar.ml
   File "bar.ml", line 1, characters 8-33:
   Unbound value true

But when you substitute 1=1 for true this works as expected. Can true 
not be used as literal in expr quotations?

Thanks,

Maas


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Re: [Caml-list] possible camlp4 problem/bug with literal booleans in expr quotations.

[Daniel de Rauglaudre]

Hi,

On Thu, Jan 09, 2003 at 12:18:19PM +0100, Maas-Maarten Zeeman wrote:

>    EXTEND
>      expr: LEVEL "expr1"
>        [ [ "forever"; body=expr ->
>               <:expr< while true do { $body$ } >> ] ];
>    END;;

Not "true", but "True": in Revised syntax, which is used in quotations
of syntax trees, the constructors "True" and "False" must start with
an uppercase letter.

If you write it with a lowercase letter, the generated syntax tree
will represent the *variable* (not the *constructor*) named "true",
which does not exist in OCaml.

-- 
Daniel de RAUGLAUDRE
http://cristal.inria.fr/~ddr/
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