Ahouxs.123
net.unix-wizards
utzoo!decvax!harpo!floyd!vax135!houxi!houxv!houxs!hansen
Mon May 3 09:26:30 1982
Re: Re: Caveat Hackor (cc generates bad code for int *= float)
Re: `10.0 times 0.1 is hardly ever 1.0' *
* Kernighan and Plauger, "The Elements of Programming Style,"
Second Edition, McGraw-Hill, New York, 1978.
Yes, but that is because 0.1 CANNOT be stored as an exact equivalent in any
binary base. However, 0.5 (2^-1) CAN be, and multiplying 0.5 times 2 should
ALWAYS yield 1.0 in ANY base 2 machine. If you want a floating point counter
between 0 and 1.0, everyone (or should, if they've been programming any
length of time) knows that 0.125 is much preferable to 0.1. This of course
assumes that you are programming on a binary based machine, and not a
tertiary or otherwise based machine. (Anyone ever seen one of these?)
The real point of the previous note is that the code produced by "i *= f" is
supposed to be exactly equivalent in result as "i = i * f." In this case, it
is NOT, and is therefore a bug.
Sincerely,
Tony Hansen
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