Hui Zhou wrote:
On Mon, Feb 28, 2005 at 01:36:32AM +0000, Johan V. wrote:How about:
return ( a+b+c == 180 ) * (a>0) * (b>0) * (c>0) * ( 1 + (a==b) + (a==c) + (b==c) );
0 : not a triangle 1 : scalene 2 : isosceles 4 : equilateral
Very Clever! Except ...
1. Obscured 2. Wasting CPU clocks
I know it's very obscured. Think about the wasted clock cycles for a minute, the above can be implemented without conditional jumps ...
Obscured mostly because it reles on the fact that compiler treats boolean as 1 or 0, not a fact supposed to be relied on.
Wasting CPU because it asks the cpu to gothrough all the comparisons and additional multiplication and summation. If the compiler is smart enough ot optimize away multiplication of 0 and summation of 0, it goes back to the original conditional jumps' version.
(a || b || c) && ... is known to be shortcut, will (a+b+c) * ... be shortcut?
Frankly I am not sure whether gcc will optimize away those multiplications and summations. I will appreciate it if you will find out and let me know.
Cheers, -- Hui Zhou -- http://linuxfromscratch.org/mailman/listinfo/lfs-chat FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
