[Pharo-project] digitAt: issue

Stéphane Ducasse stephane.ducasse at inria.fr
Mon May 2 17:30:37 CEST 2011


open an issue and propose a path to get there

Stef

On May 2, 2011, at 3:34 PM, Camillo Bruni wrote:

> DigitAt: is a horrible name then, should rather be bitAt:.
> 
> the digitAt: implementation you're looking for:
> 
> 	^ self // (10 raisedTo: index - 1) \\ 10
> 
> thats quite short :)
> 
> On 2011-05-02, at 11:35, Bernat Romagosa wrote:
> 
>> Ouch, understood!
>> 
>> Then what would be the proper way to address a decimal digit in a number? I can only think of (bigNumber asString at: index) asNumber, which is... awful.
>> 
>> 2011/5/2 Sven Van Caekenberghe <sven at beta9.be>
>> Bernat,
>> 
>> On 02 May 2011, at 11:13, Bernat Romagosa wrote:
>> 
>> > Hi, try to run the following:
>> >
>> > (2 raisedTo: 100000) digitAt: 1
>> >
>> > The expected result (if I understood what digitAt: should return) is 9, but the message returns 0 instead. In fact, it returns 0 for any index.
>> >
>> > Is this a bug or am I missunderstanding how digitAt: should work?
>> >
>> > Cheers,
>> >
>> > Bernat Romagosa.
>> >
>> > p.s. My config is Pharo 1.2 with a 'Croquet Closure Cog VM [CoInterpreter VMMaker-oscog.51]' on Debian Lenny.
>> 
>> Consider,
>> 
>> 2 raisedTo: 32
>> 
>> #digitAt: for digits 1 to 4 returns 0, 5 return 1.
>> From the comments you can see that the number is looked at in base 256.
>> The above number thus has 5 digits in this base, four are zero and the highest one is one.
>> Furthermore, the first digit is the lowest one.
>> If you inspect the number it might become clearer.
>> 
>> Any #digitAt: has to depend on the base you use to represent the number, this one doesn't, so it seems to be useful only to return internal parts of a number.
>> 
>> HTH,
>> 
>> Sven
>> 
>> 
>> 
> 




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