From: "Cédric Foll" <cedric.foll@...>
Date: 2002-09-04T23:44:30+09:00
Subject: Re: option remember

Thanks for your answers but i don't like the way used by the pragmatic prog
(but you did great job with this book, thanks a lot !!!). It's ok but i
would like to find something more "natural".
The memoise module is to big for me, i only want to understand how it's
work. I've tried to read the module but i don't understand all because of
his size.
In the "Introduction to Python" book i'd found something very simple
(overload of __call__ for an instance of function class).
So I've tried to do something as simple.
I've wrote the folowing code and i don't really understand why it doesn't
work.
---------------
def fib(n) #a function with double recursion
  if n < 2
    1
  else
    fib(n-1)+fib(n-2)
  end
end
$arg=[] #the table for allready computed variables
def remember(func)
 p method(func).call(5) #it's work
 newfunc = Proc.new { |n|
  $arg[n]=method(func).call(n) if $arg[n]==nil
  return $arg[n]
 }
 return newfunc
end

fib2=remember(:fib)
p fib2.call(10)
--------------
i get a "in `call': return from proc-closure (LocalJumpError)"
C:\ruby>ruby -v
ruby 1.6.5 (2001-09-19) [i386-cygwin]
--------------
1) Why it doens't work ?
I think that the solution should be the use of 'binding', i've read the
paragraph "Calling Methods Dynamically" in prag prog but i don't understand.
2) Why fib.type (or self.fib.type) doesn't work? I've understood (even if i
don't like) the python way where there is a class "function", but i don't
understand the ruby way.
I've read that the difference between a function and a method is only from
where u call it (method from outside, function inside the class). I'm right
? How access to functions ?
I would like to read something clear about the difference between proc,
method and there use. An article about that exists ?
Especially the use of ':', '&', the class Symbol, Proc, Method, Block,
Binding.

Regards.

--
Cedric Foll
cedric dot foll at laposte dot net