Oh, just something I forgot to mention: ScaledDecimal should behave the way you expect. 1.3s1 = (13/10). -> true. 1.3s2*1.3s2 = 1.69s2. -> true 1.3 * 1.3 = 1.69. -> false Nicolas 2009/7/7 Nicolas Cellier <nicolas.cellier.aka.nice@gmail.com>:
Hi Hernan, This is the new Behavior of Float comparison and it is desired.
1) 1.3 is represented in machine as (1.3 significandAsInteger printStringRadix: 2) , '.0e' , (1.3 exponent - Float precision + 1) printString. -> '2r10100110011001100110011001100110011001100110011001101.0e-52'
Or if you prefer: (1.3 asTrueFraction numerator printStringBase: 2) , '/' , (1.3 asTrueFraction denominator printStringBase: 2). -> '10100110011001100110011001100110011001100110011001101/10000000000000000000000000000000000000000000000000000'
As you can see, this is quite different from 13/10.
However, you can test (13/10) asFloat = 1.3 and that happens to be true, but that won't always be true.
2) comparing Float with strict equality is a dangerous game. Floating point operation are inherently inexact and thus asserting an exact equality is considered a bad practice.
3) basing comparisons and equality tests on inexact arithmetic rather than on exact arithmetic leads to weird behaviours. See http://bugs.squeak.org/view.php?id=3374
So i do not consider this fragment of code alone as a bug but as a feature. There might be some code depending on the old behaviour that can eventually break. If you have such an example in true application, I'm interested. I think we'd better fix such code to not rely on exact equality...
Cheers.
Nicolas
2009/7/7 Hernan Wilkinson <hernan.wilkinson@gmail.com>:
I added this new issue that happens on the latest image. I'm posting it here because I think it is an important bug because it affects the number model. The problem is related with all fractions who's denominator is not power of two. (130/100 = 1.3 or 1/5 = 0.2, etc) (See
Float>>adaptToFraction: rcvr andCompare: selector where it does   ....   "Try to avoid asTrueFraction because it can cost"   selector == #= ifTrue: [    rcvr denominator isPowerOfTwo ifFalse: [^false]].
  ...)
Hernan.
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