[m-rev.] for review: pseudo-typeinfo RTTI in Mercury

[Fergus Henderson]

On 10-Apr-2002, Zoltan Somogyi <zs at cs.mu.OZ.AU> wrote:
> 
> compiler/rtti.m:
> 	Add new, purely Mercury data structures for representing typeinfos
> 	and pseudo-typeinfos, designed both for efficient interpretation
> 	and as a source for the generation of static data structures in C.
> 
> compiler/pseudo_type_info.m:
> 	Delete the type definitions here, since they are superseded by the new
> 	definitions in rtti.m.

> Index: compiler/rtti.m
...
> +:- type var_arity_ctor_id
> +	--->	pred_type_info
> +	;	func_type_info
> +	;	tuple_type_info.
> +
> +:- type rtti_type_info
> +	--->	plain_arity_zero_type_info(
> +			rtti_type_ctor
> +		)
> +	;	plain_type_info(
> +			rtti_type_ctor,
> +			% This list should not be empty; if it is, one should
> +			% use plain_arity_zero_type_info instead.
> +			list(rtti_type_info)	
> +		)
> +	;	var_arity_type_info(
> +			var_arity_ctor_id,
> +			list(rtti_type_info)
> +		).
> +
> +:- type rtti_pseudo_type_info
> +	--->	plain_arity_zero_pseudo_type_info(
> +			rtti_type_ctor
> +		)
> +	;	plain_pseudo_type_info(
> +			rtti_type_ctor,
> +			% This list should not be empty; if it is, one should
> +			% use plain_arity_zero_pseudo_type_info instead.
> +			list(rtti_maybe_pseudo_type_info)
> +		)
> +	;	var_arity_pseudo_type_info(
> +			var_arity_ctor_id,
> +			list(rtti_maybe_pseudo_type_info)
> +		)
> +	;	type_var(int).
> +
> +:- type rtti_maybe_pseudo_type_info
> +	--->	pseudo(rtti_pseudo_type_info)
> +	;	plain(rtti_type_info).
> +
> +:- type rtti_maybe_pseudo_type_info_or_self
> +	--->	pseudo(rtti_pseudo_type_info)
> +	;	plain(rtti_type_info)
> +	;	self.

These should all be documented -- what the types represent,
what each alternative constructor represents, what they're used
for, and why there is so much redundant duplication.

Also, I suggest s/var_arity_ctor_id/var_arity_type_ctor_id/

> Index: compiler/pseudo_type_info.m
> -:- type pseudo_type_info
> -	--->	type_var(int)
> -			% This represents a type variable.
> -			% Type variables are numbered consecutively,
> -			% starting from 1.
> -	;	type_ctor_info(
> +	% pseudo_type_info__construct_type_info(Type, TypeInfo)
>  			%
> -			% This represents a zero-arity type,
> -			% i.e. a type constructor with no arguments.
> -			%
> -			rtti_type_ctor
> -		)
> -	;	type_info(
> -			%
> -			% This represents a type with arity > zero,
> -			% i.e. a type constructor applied to some arguments.
> -			% The argument list should not be empty.
> -			%
> -			rtti_type_ctor,
> -			list(pseudo_type_info)
> -		)
> -	;	higher_order_type_info(
> -			%
> -			% This represents a higher-order or tuple type.
> -			% The rtti_type_ctor field will be pred/0,
> -			% func/0 or tuple/0; the real arity is 
> -			% given in the arity field.
> -			%
> -			rtti_type_ctor,
> -			arity,
> -			list(pseudo_type_info)
> -		)
> -	.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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