From: Shashank Date <sdate@...>
Date: 2003-07-07T05:33:04+09:00
Subject: Re: Freezing an arbitary object


"Aryeh M. Frierdman" <aryeh@m-net.arbornet.org>
> foo=1
> test.invariant(foo)
> foo+=1          # should produce an error and exit

This will work like you want if you make

  foo = [1,2,3]
  test.invariant(foo)
  foo[0] = 2

Now, with foo = 1 even foo.freeze will not work:

#-------------------------------------------------------------
  C:\>ruby -ve "foo = 1; foo.freeze; foo = 2; puts foo; "
  ruby 1.8.0 (2003-06-23) [i386-mswin32]
  2

  C:\>ruby -e "foo = [1]; foo.freeze; foo = 2; puts foo; "
  2

  C:\>ruby -e "foo = [1]; foo.freeze; foo[0] = 2; puts foo; "
  -e:1:in `[]=': can't modify frozen array (TypeError)
        from -e:1
#-------------------------------------------------------------

HTH,
-- shanko