From: Logan Capaldo <logancapaldo@...>
Date: 2006-05-07T03:45:49+09:00
Subject: Re: What do you say to log2 to Math module?


On May 6, 2006, at 2:39 PM, M. Edward (Ed) Borasky wrote:

> Am I missing something here? In any programming language, define the
> constant
>
> Multiplier = 1.0/logtoanybase(2)
>
> Then
>
> log2(x) = Multiplier*logtoanybase(x)
>
> You have to compute the Multiplier *once*. My guess is that most
> implementations of other languages compute logs to only one base,
> probably the natural (base e) log, and compute logs to all other bases
> by doing this multiplication every time you call them -- or worse, not
> pre-computing the Multiplier and doing a divide every time, which  
> takes
> longer and is less accurate.
>
>
I'm sure they do, he would just like to avoid typing

module Math
   Log2Multiplier = 1.0 / self.log(2.0)
   def self.log2(x)
       self.log(x) * Log2Multiplier
   end
end

everytime he writes a new program


>
> Minkoo Seo wrote:
>> Hi list.
>>
>> I'm using ruby for my research purpose, and as everyone knows
>> computer science is all about log function whose base is 2.
>>
>> Unfortunately, Math module does not contain log2 though it has
>> log10. What do you think about adding log2 to Math?
>>
>> Yes, I know that adding log2 is way so simple because I can
>> open Math module and add log2 method, but I've had to that ALWAYS.
>>
>> Sincerely,
>> Minkoo Seo
>>
>
> -- 
> M. Edward (Ed) Borasky
>
> http://linuxcapacityplanning.com
>
>