[m-rev.] diff: implement concat_string_list for .NET

[Zoltan Somogyi]

On 16-Feb-2003, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> +	% This type is for strings which may contain embedded null characters.
> +:- type string_with_0s ---> string_with_0s(string).

This is wrong. If you define an abstract data type, it must contain not only
the character array ("string") but also its length.

> +% This version is only used if there is no matching foreign_proc version.
> +% Note that this version only works if the Mercury implementation's
> +% string representation allows strings to contain embedded null
> +% characters.  So we check that.
> +concat_string_list(StringsList, _Len, string_with_0s(StringWithNulls)) :-
> +	(	
> +		char__to_int(NullChar, 0),
> +		NullCharString = string__char_to_string(NullChar),
> +		string__length(NullCharString, 1)
> +	->

I don't believe this test will succeed on any version of the current Mercury
implementation.

The reason why I used C code to do the concatenation in the first place
is that with a very few exceptions (such as string__index), the predicates
in the string module all assume that strings are null terminated.
String__length certainly does.

Zoltan.
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