From: Jean-Hugues ROBERT <jean_hugues_robert@...>
Date: 2004-05-02T03:02:00+09:00
Subject: Why no Proc##[]=() ? Why no Proc##replace() ?

Hi,

Looking at lvalues in Ruby I learned a lot. I thought Proc
instances could be turned into lvalues too, so I tried:

class Proc
   def []=(*args) self[*args] end
end

pp = proc { |*x| @val = x[0] unless x.empty? ; @val }
pp[] = 1 # => 1
p pp[]   # => 1

Ruby's cool, no doubts.
Is this worth a RCR ?

Then I tried to rebuilt my version of a Pointer class at
http://www.c2.com/cgi/wiki?SinisterSchemeSampleInRuby
with what I had learnt.

class Pointer < Proc
   def initialize( &block ) ref( &block) end
   def ref( &block )
     lvalue = block.call()
     tmp = eval( "proc { |*x| #{lvalue} = x[0] unless x.empty? ; #{lvalue} 
}", block)
     self.replace tmp
   end
   def to_s() self[].to_s() end
   def inspect() "<Pointer>#{self[].inspect()}" end
end

That would be considerably simpler, the body makes 8 lines versus 16.
But it does not work, there is no Proc##replace()

Yours,

Jean-Hugues





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