From: Eleanor McHugh <eleanor@...>
Date: 2008-07-02T23:06:06+09:00
Subject: Re: Arithmetic oddity

On 2 Jul 2008, at 15:01, Robert Klemme wrote:
> 2008/7/2 Minh Tran <mtgred@gmail.com>:
>> I tried with
>>
>> s = l.map {|e| (e**2).to_s.to_f}
>>
>> instead of
>>
>> s = l.map {|e| e**2}
>>
>> and it now works.
>
> But it works only accidentally!  This is likely to break soon again.
>
>> It doesn't look very elegant though to need such kind of hacking to  
>> make
>> it base operator to work as expected.
>
> No, no, no!  The operator works as expected.  There is even an IEEE
> standard defining how floating point math has to behave. You must
> *never* rely on == when doing float math.  In this case you rather
> need to do either of these
>
> - resort to decimal math with BigDecimal
>
> - define equality as a max difference ("epsilon") between two float
> values and test that

Phrased much better than my replies :)


Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net
----
raise ArgumentError unless @reality.responds_to? :reason