I found it a lot of fun... trying to understand the code and see how it works. Thank you for this ingenious way to solve the problem. I have learned that there are some special method names, +@, -@, etc. which are invoked by writing them before the object...mmmm interesting. But seems it only works with +@ and -@... where could I find more information about it? Can I create other XXX@ methods? PS: When you create the object IinitContainer(@value, self) (lines 12 and 22).... the value of @value could be anything. It doesn't matter if you put +@value or -@value or nil or whatever because it won't be used. ;-) Thank you very much! :-) -------------------------------------- 1 #!/usr/bin/env ruby 2 3 class IntContainer 4 def initialize(value, origref=nil) 5 @value = value 6 @origref = origref 7 end 8 9 def +@ 10 case @origref 11 when nil 12 IntContainer.new(@value, self) 13 else 14 @origref.value += 1 15 @origref 16 end 17 end 18 19 def -@ 20 case @origref 21 when nil 22 IntContainer.new(@value, self) 23 else 24 @origref.value -= 1 25 @origref 26 end 27 end 28 29 attr_accessor :value 30 31 def method_missing(meth, ...) 32 IntContainer.new(@value.send(meth, ...)) 33 end 34 35 def inspect(...) = @value.inspect(...) 36 def to_s(...) = @value.to_s(...) 37 end 38 39 int = IntContainer.new(5) 40 41 puts int + 10 42 puts (++int) 43 puts (--int) -------------------------------------- Enviado con Proton Mail correo electrónico seguro. ------- Original Message ------- El martes, 29 de noviembre de 2022 a las 20:10, hmdne <hmdne@airmail.cc> escribió:
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!
Enviado desde Proton Mail móvil
-------- 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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