From: Morton Goldberg <m_goldberg@...>
Date: 2007-02-08T09:08:38+09:00
Subject: Re: Adding Math.log2 and Math.logn to the core library.

On Feb 7, 2007, at 6:20 PM, Phrogz wrote:

> On Feb 7, 2:57 pm, Keynan Pratt <key...@howe.textdrive.com> wrote:
>> perhaps it would be wiser to add
>>
>> def log_(n, x)
>>   log x / log n
>> end
>>
>> so that any log base may be used.
>
> Other than changing the order of parameters (which I'm personally
> ambivalent about, and would certainly accept this order if that's how
> most other libraries do it) and changing the name to end in an
> underscore (which I'm not sure I like), what are you proposing that I
> wasn't? Simply that we ONLY add the log-base-n capability that I
> described, without a specific method for log-base-2 calculations?

Well, I can find examples with the base first or second. Perhaps for  
Ruby it would most idiomatic to define log as follows

    def Math.log(x, b=Math::E); ... ; end

as the core method with log10 and log2 handled (for performance) as  
special cases within this method. Given that, I would still want Math  
to implement log10 and log2 methods for convenience.

If we were to go with a two argument log, I prefer the "logb" name to  
"logn" because "n" suggests an integer and the base doesn't have to  
be an integer (e.g., it could be Math::E).

Regards, Morton