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[Caml-list] camlp4: LIST1 construct on record patterns
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Date: -- (:)
From: Jeff Henrikson <jehenrik@y...>
Subject: [Caml-list] camlp4: LIST1 construct on record patterns
In camlp4, I don't seem to be able to break apart a record pattern in any way.  I must not understand how to use LIST1 properly:



let try_extend _ =
  let cons = "Bogus" in
  let test_label_eq = Grammar.Entry.find expr "test_label_eq" in
  let lbl_expr_list = Grammar.Entry.find expr "lbl_expr_list" in
  EXTEND
    expr: LEVEL "simple"
    [ [ $cons$; "{"; memb = LIST1 lbl_expr_list SEP ";" ; "}" ->
          <:expr<{$list:memb$}>> ] ]
    ;
  END;;

try_extend "junk";;

...
      [ [ $cons$; "{"; memb = LIST1 reenter SEP ";" ; "}" ->
            <:expr<{$list:memb$}>> ] ]
                          ^^^^
      ;
    END;;
This expression has type Obj.t list but is here used with type
  (MLast.patt * MLast.expr) list


Isn't an Obj.t a completely opaque meaningless entity?

Substituting test_label_eq for lbl_expr_list makes no difference.  I got those identifiers by running:

Grammar.Entry.print expr;;

which doesn't tell me the meaning of test_label_eq, and

Grammar.Entry.print (Grammar.Entry.find expr "test_label_eq");;

doesn't tell me anything either.  Do I just have to go read the source code to know their meaning?  I would have except I guess it
doesn't come default now that camlp4 is part of ocaml.


Jeff Henrikson




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