From: Rick DeNatale <rick.denatale@...>
Date: 2009-11-01T06:19:01+09:00
Subject: Re: Ruby doesn't implement x++ for Fixnum's because ???

On Fri, Oct 30, 2009 at 6:20 PM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> On 10/30/2009 08:03 PM, Rick DeNatale wrote:

> How their behavior is defined is completely up to the language designer.
>  You could make "a++" syntactic sugar for
>
> (_tmp = a; a = a + 1; _tmp)
>
> in the same way as "a += 1" is syntactic sugar for "a = a + 1" or "a ||= 10"
> is syntactic sugar for "a || a = 10".  In fact the sequence in brackets
> above would be a completely reasonable way to do it in Ruby: you could use
> "a++" in a similar way as in C++ and Java without sacrificing Fixnum's
> immutability.

And I would argue that you still can't implement ++ for fixnum since
there isn't a ++ method, any more than there is a += method.

> But: you would hide the assignment in the syntactic sugared version and this
> could lead to unexpected behavior, like

Which I think gets to the fundamental difference.

In C/C++ an integer variable is just a bit-string of a particular
length interpreted as a signed (probably 2s complement) integer, and
++ is a operator on the variable which twiddles those bits.

In Ruby and languages of its ilk, a variable is a reference to an
object, and can only be modified by an assignment, not by a method of
the object it happens to be referencing at the moment, whether that
object is mutable or not.

-- 
Rick DeNatale

Blog: http://talklikeaduck.denhaven2.com/
Twitter: http://twitter.com/RickDeNatale
WWR: http://www.workingwithrails.com/person/9021-rick-denatale
LinkedIn: http://www.linkedin.com/in/rickdenatale