matthew

why don't you call your method numberOfZeros? because it is talking 
better to me.
Richard can you review the code and tests of matthew and this way I 
will take on my time to add that in the 3.9
distribution if there is a consensus.

Stef


On 10 déc. 04, at 07:02, Matthew S.Hamrick wrote:

> Good recommendation. I've always been a fan of test-first 
> development... probably should have done this earlier.  Attached is:
>
> a. a change-set for Integer that includes a version of popCount that 
> throws an error if you invoke it on a negative number.
> b. a SIUnit test subclass that does simple testing and has some 
> documentation
>
> <Integer.msh.2.cs><PopCountTest.msh.1.cs>
>
> On Dec 9, 2004, at 4:33 AM, stéphane ducasse wrote:
>
>> Matthew
>>
>> it would be a really nice occasion to document your code with a 
>> couple of SUnit tests.
>> http://www.iam.unibe.ch/~ducasse/Programmez/OnTheWeb/SUnitEnglish2.pdf
>> It should take you 5 min and this way you will help the people 
>> looking at it.
>>
>> Stef
>>
>>
>> On 9 déc. 04, at 02:13, Richard A. O'Keefe wrote:
>>
>>> "Matthew Hamrick" <Matthew.Hamrick at gibson.com> wrote
>>> (edited somewhat to take fewer lines and be more ASCII-friendly):
>>>
>>> 	popCount
>>> 	 "Answers the number of bits set in an integer."
>>> 	 | t1 t2 |
>>> 	 t1 := self.
>>> 	 t2 := 0.
>>> 	 [t1 == 0] whileFalse: [t1 := t1 bitAnd: t1 - 1. t2 := t2 + 1].
>>> 	 ^ t2
>>>
>>> What is this supposed to do when the number is negative?
>>>
>>>     -1 bitAnd: -2	=> -2
>>>     -2 bitAnd: -3	=> -4
>>>     -4 bitAnd: -5	=> -8
>>>
>>> In Squeak 3.6-5429-full.image, (-1 popCount) eventually terminates 
>>> because
>>>     m := -1 bitShift: 31.
>>>     m := m bitAnd: m - 1
>>> sets m to 0, instead of to the correct value (-1 bitShift: 32).
>>> First time I've ever had Squeak give me the wrong answer for an
>>> integer calculation.
>>>
>>> Notionally, a Squeak negative integer has infinitely many 1 bits, so 
>>> I
>>> suggest
>>>
>>>     popCount
>>>       "self >= 0 => answer the number of 1 bits in the binary 
>>> representation.
>>>        self <  0 => answer the number of 0 bits in the binary 
>>> representation.
>>>        Two's complement is assumed.
>>>       "
>>>       |m n|
>>>       (m := self) < 0 ifTrue: [m := -1 - self].
>>>       n := 0.
>>>       [m == 0] whileFalse: [m := m bitAnd: m-1. n := n+1].
>>>       ^n
>>>
>>> Another alternative would be to make it an error to send #popCount 
>>> to a
>>> negative integer.
>>>
>>>
>>
>>
>