camlp4 parser accepts more than its grammar?

camlp4 parser accepts more than its grammar?

[Jake Donham]

Hi list,

I expected the following program to fail with a parse error, but it
happily ignores the extra '+'. I would be grateful if someone could
point out what I'm doing wrong. Thanks,

Jake


open Camlp4.PreCast;;

let expr = Gram.Entry.mk "expr";;
let stmt = Gram.Entry.mk "stmt";;

EXTEND Gram
  expr: [[
    x = expr; "+"; y = expr -> x + y
  | x = INT -> int_of_string x
  ]];
  stmt:
  [[ e = expr; ";"; `EOI -> e ]];
END;;

prerr_endline (string_of_int (Gram.parse_string stmt Loc.ghost "2 + 1 + ;"))

Re: [Caml-list] camlp4 parser accepts more than its grammar?

[Nicolas Pouillard]

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Excerpts from Jake Donham's message of Thu Jun 26 23:10:20 +0200 2008:
> Hi list,
> 
> I expected the following program to fail with a parse error, but it
> happily ignores the extra '+'. I would be grateful if someone could
> point out what I'm doing wrong. Thanks,

Nothing wrong from you, that's a camlp4 known bug (PR#4551, PR#4513...).

> open Camlp4.PreCast;;
> 
> let expr = Gram.Entry.mk "expr";;
> let stmt = Gram.Entry.mk "stmt";;
> 
> EXTEND Gram
>   expr: [[
>     x = expr; "+"; y = expr -> x + y
>   | x = INT -> int_of_string x
>   ]];
>   stmt:
>   [[ e = expr; ";"; `EOI -> e ]];
> END;;
> 
> prerr_endline (string_of_int (Gram.parse_string stmt Loc.ghost "2 + 1 + ;"))
> 

-- 
Nicolas Pouillard aka Ertai

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Re: [Caml-list] camlp4 parser accepts more than its grammar?

[Till Varoquaux]

2008/6/27 Nicolas Pouillard <nicolas.pouillard@gmail.com>:
> Excerpts from Jake Donham's message of Thu Jun 26 23:10:20 +0200 2008:
>> Hi list,
>>
>> I expected the following program to fail with a parse error, but it
>> happily ignores the extra '+'. I would be grateful if someone could
>> point out what I'm doing wrong. Thanks,
>
> Nothing wrong from you, that's a camlp4 known bug (PR#4551, PR#4513...).
>
>> open Camlp4.PreCast;;
>>
>> let expr = Gram.Entry.mk "expr";;
>> let stmt = Gram.Entry.mk "stmt";;
>>
>> EXTEND Gram
>>   expr: [[
>>     x = expr; "+"; y = expr -> x + y
>>   | x = INT -> int_of_string x
>>   ]];
>>   stmt:
>>   [[ e = expr; ";"; `EOI -> e ]];
>> END;;
>>
>> prerr_endline (string_of_int (Gram.parse_string stmt Loc.ghost "2 + 1 + ;"))
>>
>
> --
> Nicolas Pouillard aka Ertai
>
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>


Note that you might even have suprises when using the standard Ocaml
parser: I consider grammar more like a guideline then an actual
specification.

type t = A of int | false of float

Till

Re: [Caml-list] camlp4 parser accepts more than its grammar?

[Arthur Chan]

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> type t = A of int | false of float
>
>
That is so evil.

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Re: [Caml-list] camlp4 parser accepts more than its grammar?

[blue storm]

On 7/1/08, Arthur Chan <baguasquirrel@gmail.com> wrote:
>> type t = A of int | false of float
>>
>>
> That is so evil.
>

But it won't break any syntaxic sugar, as with
  type 'a list = () | :: of 'a * 'a list

Sadly, camlp4o reject these.