[Pharo-project] digitAt: issue

Camillo Bruni camillo.bruni at inria.fr
Mon May 2 15:34:20 CEST 2011


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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