From: Chris <nemo@...>
Date: 2002-12-01T06:22:27+09:00
Subject: Re: Ruby ++, the one element and generators

The problem is simple:

Q:  Why isn't "x++" just syntax sugar for "x += 1"?

A:  Because in C, for example, "x++" doesn't mean "x += 1"!

  int x, y, z;

  x = 5;
  y = x++;     //  y == 5
  x = 5;
  z = x += 1;  //  z == 6

It would confuse and upset C programmers, so best not to put it in.


Remember, the following code could only be intended to mean two things:

  x = 5
  x++

Either you want "++" to be a method, so you really meant so call the "++"
method of the object 5; or you want "++" to be syntax sugar, which we have
already seen is a bad idea (confusing and counter-intuitive).

However, what does it mean to call 5's "++" method?  Again, there are only
two reasonable things you could mean:  either you want the method to return
6, or you want 5 to change it's value to 6.  I thing we would all agree that
the latter is absurd (is anyone arguing that they want 5 == 6 ??), so that
leaves the former.  Let's say we could define it like so:

  class Fixnum
    def ++
      self+1
    end
  end

  x = 5
  y = x++  #  So y == 6, which is 'wrong' from a C standpoint.
  x        #  And x is still 5.  Terrible.


----- Original Message -----
[snip]
In other words, ++ is an operator that replaces a reference to one object
with a reference to the next object. This operation may or may not be an
inplace operation.
----------------------------

It *cannot* be in-place, because then 5 would equal 6.  This is BAD.


----------------------------
In algebraic terms, there is no 'one' element for Real numbers
----------------------------

Uh, where did you get that idea?  The real number are a field.  Check out
your field axioms again.  There's an axiom there just to state the existence
of '1'.  (This doesn't seem relevant to your argument or mine...  :)  but I
had to point that out.)


----------------------------
No we could equally well write

a++ as a synonym for
a = a.next
----------------------------

No, we couldn't!  The only reason anyone wants a "++" operator is because
they like it from C/C++/Java/etc.  However, if it didn't work like it does
in other languages, it would be terrible!  We'd never hear the end of it!
(Hmm...  :) )  Like I said, if we can't implement it *exactly* like it works
in C, then it's a bad idea.  Surely no one disagrees with this?!

"++" is a relic from a language working too close to the processor
instructions.

Chris