On 9/2/10 Thu Sep 2, 2010 2:00 PM, "Jim" <jim@lowcarbfriends.com>
scribbled:
> On 9/2/2010 4:15 PM, Jim Gibson wrote:
>> My advice is to stay away from these modules unless you know what you are
>> doing. I find that double-precision floating-point arithmetic is always good
>> enough. I have been programming in scientific and technical fields for 40
>> years and have yet to need extended-precision arithmentic.
>>
>> If, on the other hand, you are working with large, financial transactions or
>> cryptography, you may need these modules. If that is the case, however, you
>> probably shouldn't be looking for help on a Perl beginner's list.
>>
>> I just do not want anybody to get the impression that these modules are
>> needed for accurate arithmetic in Perl and that standard Perl arithmetic
>> operations are inaccurate.
>
> I'm open to more advice. How would you rewrite my original toy code?
I wouldn't. It doesn't contain any errors. What you are seeing is the
expected behavior. The internal representation of most floating-point
numbers is approximate. If you print out binary floating-point numbers at
enough precision you will see differences from decimal representations. If
you are using double-precision floating-point, the accuracy is about 16
decimal places. If you need more accuracy than that, then you need to use
extended precision. But those applications are rare.
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