From: Ben Giddings <bg-rubytalk@...>
Date: 2003-09-15T07:29:40+09:00
Subject: Re: performance and style advice requested

Some style advice:

On Sunday, September 14, 2003, at 12:44  PM, Alex Martelli wrote:
> #
> # factorial, memoized via an Array
> #
> $_fact_memo=[1,1,2,6,24,120,720]

Ugh.  This is what really bothers me about python programs.  Ugly 
underscores.

> def fact(x)
>     # factorial of x (0 if x<0)
>     result = $_fact_memo[x]
>     if !result
>         return 0 if x<0
>         result = $_fact_memo[x] = x*fact(x-1)
>     end
>     return result
> end

Hmm, how about

def fact(x)
     $fact_memo[x] ||= if x<0
                          0
                       else
                          x*fact(x-1)
                       end
end

Although I'm pretty sure that a simple conditional is faster than an 
array lookup so this might be faster (and is easier to read):

def fact(x)
     return 0 if x<0
     $fact_memo[x] ||= x*fact(x-1)
end

You can take advantage of the fact Ruby expressions return their last 
value, and the return value of a function is the last expression's 
value.

The rest is more complex so I'll quit while I'm ahead.  :)

Ben