Background on why Ruby doesn't support ++

Ruby
#1

Hi All,

I’m a big Ruby fan and I’m not trying to complain.

I’m just curious as to why Ruby doesn’t support the ++ or – operators.
Is there some syntactical ambiguity that’s associated with it or
something.

Anyone know the history on this deliberate omission?

Thanks!

Adam

#2

On Wed, Aug 12, 2009 at 11:20 PM, Adam L.[email protected]
wrote:

Anyone know the history on this deliberate omission?

Matz addressed this in ruby-talk 2710:

http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/2710

HTH!
Shajith

#3

On Thu, Aug 13, 2009 at 11:31 AM, Robert
Klemme[email protected] wrote:

incremented.
Makes sense, though strictly speaking x++ could be syntactic sugar for
x+=1 or x =x +1
but this would probably be very confusing for many folks for the very
reason you gave.
Cheers
Robert

#4

Don’t forget there’s already

x.next

although there is not the orthogonal x.prev, which seems like the
Principle of Most Surprise in effect :-). One way to rectify that is
to open up Integer yourself:

class Integer
def prev
self - 1
end
end

#5

2009/8/13 Shajith C. [email protected]:

On Wed, Aug 12, 2009 at 11:20 PM, Adam L.[email protected] wrote:

Anyone know the history on this deliberate omission?

Matz addressed this in ruby-talk 2710:

http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/2710

Basically it is a consequence of the decision to make integers
immutable which makes assignment necessary for a variable which is
incremented. I guess Matz wanted to make this explicit, hence “+=”
Co.

Otherwise you need a counter class, e.g.

Counter = Struct.new :value do
def initialize(x = 0)
self.value = x
end

def plusplus
self.value += 1
end

alias incr plusplus

def minusminus
self.value += 1
end

alias decr minusminus
end

:slight_smile:

Kind regards

robert

#6

2009/8/13 Mark T. [email protected]:

self - 1
end
end

There is also #succ and #pred. But this is not the point: all of them
work by returning a different object. You can easily verify by
looking at the result’s #object_id. Operators ++ and – in C++ on the
other hand change the object (int, long etc.) itself. The difference
is whether you will have aliasing or not.

Kind regards

robert