From: David Alan Black <dblack@...>
Date: 2001-12-23T10:43:41+09:00
Subject: [ruby-talk:29332] Re: a better way?

Hi --

On Sun, 23 Dec 2001, Hal E. Fulton wrote:

> From: David Alan Black <dblack@candle.superlink.net>
>
> > Hi --
> >
> > On Sun, 23 Dec 2001, Ron Jeffries wrote:
> >
> > > I was writing a little code that cached a function value, and wound up
> > > with this:
> > >
> > > result = @@save[self]
> > > return result if result
> > >
> > > I don't see a way to do it in one line unless I'm willing to do the
> > > lookup twice. Am I missing something?
> >
> > You could do:
> >
> >    result = @@save[self] and return result
>
> Or the C-like:
>
>    if result=@@save[self] then return result end
>
> I don't fully understand your application, but I'm
> assuming you *don't* want to return a nil and
> check for it in the caller... otherwise, of course,
> you could just do:
>
>     return @@save[self]

I think the design is that some calculation will only be performed
once, then cached -- one of these guys:

  class Temp
    @@save = {}
    def fahrenheit(c)
      result = @@save[self] and return result
      puts "Performing calculation...."
      @@save[self] = c * 9 / 5 + 32
    end
  end

  t = Temp.new

  puts t.fahrenheit(100) # "Performing calculation....\n212"
  puts t.fahrenheit(100) # "212"


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav