On Aug 27, 2007, at 12:26 PM, Alan Barrett wrote:

> Thanks to all who answered my earlier questions about negative zero.
>
> Of the tools supplied with NetBSD that are capable of performing
> arbitrary arithmetic, awk seems to be the only one that prints
> negative zero as the result from simple calculations:
>
> 	$ echo $(( -1 * 0 ))
> 	0
> 	$ expr -1 \* 0
> 	0
> 	$ echo '-1.0 * 0.0' | bc
> 	0
> 	$ echo '-1.0 0.0 * p' | dc
> 	0
> 	$ echo | awk '{ print -1 * 0 }'
> 	-0
>
> Would it be OK if I commit the following patch, which ensures that
> arithmetic in awk will never yield a negative zero?

No objection from me.  Does POSIX have anything to say about this?   
What does GNU AWK do?

>
>
> --apb (Alan Barrett)
>
> Index: src/dist/nawk/tran.c
> --- tran.c	26 Jul 2006 20:46:37 -0000	1.9
> +++ tran.c	27 Aug 2007 19:12:48 -0000
> @@ -285,6 +285,7 @@ Awkfloat setfval(Cell *vp, Awkfloat f)	/
> {
> 	int fldno;
>
> +	f += 0.0;		/* normalise negative zero to positive zero */
> 	if ((vp->tval & (NUM | STR)) == 0)
> 		funnyvar(vp, "assign to");
> 	if (isfld(vp)) {

-- thorpej