From: Christopher Dicely <cmdicely@...>
Date: 2009-11-01T03:02:32+09:00
Subject: Re: Ruby doesn't implement x++ for Fixnum's because ???

On Fri, Oct 30, 2009 at 3:20 PM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> On 10/30/2009 08:03 PM, Rick DeNatale wrote:
>>
>> On Fri, Oct 30, 2009 at 11:05 AM, Robert Klemme
>> <shortcutter@googlemail.com> wrote:
>>>
>>> 2009/10/30 RichardOnRails <RichardDummyMailbox58407@uscomputergurus.com>:
>>>
>>>> I'll correct my errors and probably have a new theory subsequently.
>>>
>>> IMHO the story goes like this: absence of postfix ++ and -- is a
>>> consequence of the fact that numeric types are immutable in Ruby which
>>> makes an assignment necessary for these operators.  Although that
>>> would be doable, it would not immediately be obvious when looking at
>>> "foo++".  On the other side, "foo += 1" makes the assignment obvious
>>> while still being pretty concise (you do not have to write "foo = foo
>>> + 1").
>>
>> I think that theres a more fundamental problem with ++ in a language
>> like ruby, which has to do with the difference between objects and
>> variables.
>>
>> The c ++ and -- operators change a variable, NOT a value.
>
> 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.

I think it would make more sense, if you were going to define a "++"
syntax for Ruby, to use "a.succ" rather than "a+1", and if you are
going to create syntax which does an assignment but returns the
pre-assignment value of the variable receiving the assignment, I'd go
further and include a more general form for that, say ":=", such that
"a := b" is equivalent to "(_ = a),(a = b), _" and then define postfix
"++" such that "a++" is "a := a.succ" and prefix "++" such that "++a"
is equivalent to "a = a.succ".