[m-rev.] for review: implement float library for Java

[Ralph Becket]

James Goddard, Thursday, 11 December 2003:
> 
> +	% In hashing a float in .NET or Java, we ensure that the value is
> +	% non-negative, as this condition is not guaranteed by either API.
> +
>  :- pragma foreign_proc("C",
>  	float__hash(F::in) = (H::out),
>  	[will_not_call_mercury, promise_pure, thread_safe],
> @@ -430,7 +495,23 @@
>  	float__hash(F::in) = (H::out),
>  	[will_not_call_mercury, promise_pure, thread_safe],
>  "
> -	H = F.GetHashCode();
> +	int Code = F.GetHashCode();
> +	if( Code < 0 ) {
> +		H = Code ^ 1;
> +	} else {
> +		H = Code;
> +	}
> +").
> +:- pragma foreign_proc("Java",
> +	float__hash(F::in) = (H::out),
> +	[will_not_call_mercury, promise_pure, thread_safe],
> +"
> +	int Code = (new java.lang.Double(F)).hashCode();
> +	if( Code < 0 ) {
> +		H = Code ^ 1;
> +	} else {
> +		H = Code;
> +	}
>  ").

You need `H = -Code ^ 1' or somesuch in order to change the sign for the
negative Code cases.

Otherwise that looks great.

-- Ralph
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