From: Jim Weirich <jweirich@...>
Date: 2003-07-07T05:26:04+09:00
Subject: Re: Freezing an arbitary object

On Sun, 2003-07-06 at 15:32, Aryeh M. Frierdman wrote:
> Lets say I am doing design by contract and want to do a call like this:
> 
> test=UnitTest::new
> 
> foo=1
> test.invariant(foo)
> foo+=1          # should produce an error and exit

This last line can be rewritten ...

  foo = foo + 1

So you add 1 to a integer object which returns a new integer value (it
never modifies the original integer, it "creates" a new one).  This new
integer value is then bound to the name "foo". The previous foo object,
the frozen one, is no long accessable (through the name "foo").

-- 
-- Jim Weirich       jweirich@one.net      http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)