[m-dev.] for review: add null rval constant to MLDS

[Fergus Henderson]

On 05-Sep-2000, Tyson Dowd <trd at cs.mu.OZ.AU> wrote:
> Add a null type to MLDS.

That one looks fine.

I have just one minor comment:

> +++ compiler/mlds.m	2000/09/05 04:46:29
> @@ -1081,7 +1081,13 @@
>  			% first null character.
>  	;	multi_string_const(int, string)
>  	;	code_addr_const(mlds__code_addr)
> -	;	data_addr_const(mlds__data_addr).
> +	;	data_addr_const(mlds__data_addr)
> +			% A null value, of the given type. 
> +			% Usually this will be a pointer (mlds__ptr_type)
> +			% but it could be a place holder for a string or
> +			% a func_type.
> +	; 	null(mlds__type).

The wording of that comment could perhaps be improved slightly.
How about the following?

			% A null value, of the given type. 
			% Usually the type will be a pointer (mlds__ptr_type)
			% but it could also be string or a func_type.
			% (Null is not a valid value of type string
			% or func_type, but null values of those types
			% may be useful as placeholders in cases where the
			% value will never be used.)

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.
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