From: Dave Burt <dave@...>
Date: 2006-05-22T00:39:01+09:00
Subject: Re: I call Ducktype Violation on #to_proc! :)

Daniel Schierbeck wrote:
> Dave Burt wrote:
>> def to_proc
>>   proc {|*args| self.call(*args) }
>> end
> 
> Yes, that works (thanks!), but I think it's against Ruby spirit to
> require a certain class for a relatively high-level thing like this. I
> can see why there's not really any way around a string ultimately being
> a String object, through #to_str or #to_s, but all that's really
> required by the return value of #to_proc is an object that responds to
> #call.

You can actually use certain non-Proc objects:

irb> def say_hello_to() yield "hello" end
=> nil
irb> say_hello_to &method(:puts)
hello
=> nil

And you can also use a subclass of Proc.

  class CachedProc < Proc
  ...

... and your example would work, I think.

Getting off-topic, if I may revisit your cached_proc again -- you can
easily do without the class entirely.

def cached_proc &block
  cache = Hash.new {|h, k| h[k] = block.call(*args) }
  proc {|*args| cache[args] }
end

Cheers,
Dave