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Camlp4FoldGenerator doesn't handle well "abstract" types #5650

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vicuna opened this issue Jun 15, 2012 · 2 comments
Closed

Camlp4FoldGenerator doesn't handle well "abstract" types #5650

vicuna opened this issue Jun 15, 2012 · 2 comments

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@vicuna
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vicuna commented Jun 15, 2012

Original bug ID: 5650
Reporter: kyoDralliam
Assigned to: @bobzhang
Status: closed (set by @xavierleroy on 2015-12-11T18:21:27Z)
Resolution: fixed
Priority: normal
Severity: feature
Version: 3.12.1
Category: -for Camlp4 use https://github.com/ocaml/camlp4/issues
Tags: junior_job

Bug description

When using Camlp4FoldGenerator to create a map or fold class for a type t, you can't have not basic types without representation, for instance Num.num type.
A simple way to solve it would be for example to generate virtual method for such type and let the user have an abstract class i.e. accept

class virtual map = Camlp4MapGenerator.generated;;

(Until OCaml 4.00beta2 only the following form is accepted, without the virtual keyword)

class map = Camlp4MapGenerator.generated;;

Steps to reproduce

type t = A of in_channel

class map = Camlp4MapGenerator.generated;;

-->
File "ghost-location", line 1, characters 0-0:
Warning 17: the virtual method in_channel is not declared.
File "ghost-location", line 1, characters 0-0:
Error: This class should be virtual.
The following methods are undefined : in_channel

@vicuna
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vicuna commented Jun 18, 2012

Comment author: @bobzhang

Hi, if you are patient, I wrote a code generation frame work FAN, which is more functional and general purpose.

https://groups.google.com/d/topic/fa.caml/jUiHYhEDIZo/discussion

@vicuna
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vicuna commented Aug 5, 2013

Comment author: @bobzhang

Fixed in version 13973. Currently it would emit a warning for undeclared method name, which could be improved when I have time.

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