[ruby-talk:444017] Re: i++ does not work?

29 Nov 2022


      It isn't possible to implement i++, but it is... kinda... possible to 
implement ++i. Take a look at the following code. Just please don't use 
it in production 😉

class IntContainer
   def initialize(value, origref=nil)
     @value = value
     @origref = origref
   end

   def +@
     case @origref
     when nil
       IntContainer.new(+@value, self)
     else
       @origref.value += 1
       @origref
     end
   end

   def -@
     case @origref
     when nil
       IntContainer.new(-@value, self)
     else
       @origref.value -= 1
       @origref
     end
   end

   attr_accessor :value

   def method_missing(meth, ...)
     IntContainer.new(@value.send(meth, ...))
   end

   def inspect(...) = @value.inspect(...)
   def to_s(...) = @value.to_s(...)
end

int = IntContainer.new(5)
p int + 10
++int
p int
--int
p int

On 10/14/22 19:01, iloveruby wrote:
...
Is it posible define new method :++ to Integer class?
Thanks!
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-------- Mensaje original --------
El 14 oct 2022 4:53, Martin DeMello < martindemello@gmail.com> escribió:
i++ works in C and similar languages because a variable is a
    concrete object, representing a specific chunk of memory. i++
    increments the contents of that chunk of memory.
in ruby, a variable is a transparent reference to an object, so
    any operation on a variable is actually an operation on the object
    it points to. i++ would mean "mutate the object i points to by
    incrementing it by 1", and since numbers are immutable you cannot
    do that. on the other hand, "i += 1" is just shorthand for "i =
    i + 1", which means "point the variable i to a new object that is
    1 more than the object it currently points to", which works fine
    with ruby's semantics.
here's an illustration by contrast with strings, which do have
    mutating methods:
irb(main):001:0> a = "hello"
    => "hello"
    irb(main):002:0> b = a
    => "hello"
    irb(main):003:0> a.upcase!
    => "HELLO"
    irb(main):004:0> b
    => "HELLO"
    irb(main):005:0> i = 1
    => 1
    irb(main):006:0> j = i
    => 1
    irb(main):007:0* i++ # <- what would you expect j to be after this?
martin
On Thu, Oct 13, 2022 at 7:40 PM Henrik P <henrik@simplemail.co.in>
    wrote:
I found for a int the "++" operator doesn't work in ruby.
        such as,
i=0
        i++
not working. but instead it would write as:
i=0
        i += 1
so "++" is not supported in ruby really? thanks
$ ruby -v
        ruby 2.6.3p62 (2019-04-16 revision 67580)
        [universal.x86_64-darwin20]
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[ruby-talk:444017] Re: i++ does not work?

hmdne