From: Daniel Berger <djberg96@...>
Date: 2006-01-01T21:32:56+09:00
Subject: Re: Memoization, files and Marshal?

ara.t.howard@noaa.gov wrote:
> On Sun, 1 Jan 2006, Daniel Berger wrote:
>
> > ara.t.howard@noaa.gov wrote:
> >> On Sun, 1 Jan 2006, Daniel Berger wrote:
> >
> > <snip>
> >
> >>    harp:~ > cat a.rb
> >>    def memoize_to_file(name, file)
> >>      cache = Hash.new.update(Marshal.load(File.read(file))) rescue {}
> >>      (class << self; self; end).class_eval do
> >>         define_method(name) do |*args|
> >>            unless cache.has_key?(args)
> >>              cache[args] = method(name).call(*args)
> >>              File.open(file, "wb+"){|f| Marshal.dump(cache, f) }
> >>            end
> >>            cache[args]
> >>         end
> >>      end
> >>    end
> >>
> >>    def fib(n)
> >>     return n if n < 2
> >>     fib(n-1) + fib(n-2)
> >>    end
> >>
> >>    memoize_to_file "fib", "fib.cache"
> >>    n = fib 10
> >>    p n
> >
> > As is, I get a stack level too deep error on Windows.  If I change the
> > "cache[args] =" to "cache[args] ||=", I always get back nil.
> >
> > I'm probably being thick here, but any help is appreciated.
>
> sorry, don't know how that's running on linux in the first place... you need:
>
>    --- a.rb	2005-12-31 20:30:59.000000000 -0700
>    +++ b.rb	2005-12-31 20:31:10.000000000 -0700
>    @@ -1,9 +1,10 @@
>     def memoize_to_file(name, file)
>    +  meth = method(name)
>       cache = Hash.new.update(Marshal.load(File.read(file))) rescue {}
>       (class << self; self; end).class_eval do
>          define_method(name) do |*args|
>             unless cache.has_key?(args)
>    -          cache[args] = method(name).call(*args)
>    +          cache[args] = meth.call(*args)
>               File.open(file, "wb+"){|f| Marshal.dump(cache, f) }
>             end
>             cache[args]
>
> with that it works for me on linux and windows.
>
> cheers.
>
> -a
> --
>

Thanks, that did the trick nicely.  It's now part of memoize 1.2.0. :)

Regards,

Dan