On Mon, 19 Mar 2007, Hugo Ferreira wrote:
>
> Hello,
>
> I have come across a weirdness in camlp4. Maybe someone can help with
> this puzzle.
>
> I have the following extension:
>
> let expand_term_list loc l =
> let nl = <:expr< [] >> in
> let nl = List.fold_right (fun h t ->
> <:expr< [$h$::$t$] >>
> ) l nl in
> <:expr<
> do {
> List.iter (fun i -> print_endline i) $nl$
> }
> >>
>
> EXTEND
> Pcaml.expr: [
> [
> "|" ; l = LIST0 Pcaml.expr SEP ";" ; "|"->
> expand_term_list loc l ] ];
> END;;
Didn't you forget the brackets around the list?
Like this:
EXTEND
Pcaml.expr: [
[
"|" ; "["; l = LIST0 Pcaml.expr SEP ";" ; "]"; "|"->
expand_term_list loc l ] ];
END;;
> I compile the source below with the extension:
>
> ....
>
> let t1 =
> List.iter (fun i -> print_endline i) ["1"; "f(X,Y)"; "g(X,Y)"; "4"]
> in
> ()
>
> And the execution gives me:
>
> 4
>
> If I generate the original and revised syntax output using the extension
> above using for example:
>
> camlp4o -I . pr_o.cmo pa_$(NAME).cmo $(PROG).ml -o $(PROG).ppo
> camlp4o -I . pr_r.cmo pa_$(NAME).cmo $(PROG).ml -o $(PROG).ppr
>
> I get for $(PROG).ppo
>
> ...
> let t1 =
> List.iter (fun i -> print_endline i) ["1"; "f(X,Y)"; "g(X,Y)"; "4"]
> in
> ()
>
> which is what I expect for the original syntax... but for the revised
> syntax $(PROG).ppr I get:
>
> let t1 =
> do {
> print_string "Not implemented for list ";
> List.iter (fun i -> print_endline i)
> [do { "1"; "f(X,Y)"; "g(X,Y)"; "4" }]
> }
> in
> ()
>
> which ... to say the least is *not* what I expected. This explains why I
> initially though I had but one Pcaml.expr and not a list of those. What
> seems to be happening is that the revised syntax is used to generate the
> code and this is wrong.
>
> Can anyone tell me what mess I have done?
>
> TIA,
> Hugo Ferreira.
>
>
>
>
> Hugo Ferreira wrote:
>> Hello,
>>
>> I would like to convert an Ocaml expression:
>>
>> let t1 = | ["f(X,Y)"; "g(X,Y)"] | in ()
>>
>> to:
>>
>> let t1 =
>> List.iter (fun i -> print_endline i) ["f(X,Y)"; "g(X,Y)"]
>> in
>> ()
>>
>> To do this I use:
>>
>> let expand_term_list loc l =
>> let nl = <:expr< [] >> in
>> let nl = List.fold_right (fun h t ->
>> <:expr< [$h$::$t$] >>
>> ) l nl in
>> <:expr<
>> do {
>> List.iter (fun i -> print_endline i) $nl$
>> }
>> >>
>>
>> EXTEND
>> Pcaml.expr: [
>> [
>> "|"; l = LIST0 Pcaml.expr SEP ";" ; "|" -> expand_term_list loc l ]
>> ];
>> END;;
>>
>>
>> Unfortunately the output I get is:
>>
>> let t1 =
>> List.iter (fun i -> print_endline i) [["f(X,Y)"; "g(X,Y)"]]
>> in
>> ()
>>
>> As I understand it, we have to do list construction ourselves seeing as
>> we have no quotations for this. But it seems that the parameter "l" I am
>> passing to the function "expand_term_list" is an AST element and not a
>> list of AST nodes. How do I actual get the list elements?
>>
>> TIA.
>> Hugo F.
>>
>>
>>
>>
>>
>>>
>>
>
>
> >
--
Martin Jambon
http://martin.jambon.free.fr
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