Computer Science Canada

Strange things happening in my Int class
Author:  Clayton [ Fri Nov 03, 2006 9:37 pm ]
Post subject:  Strange things happening in my Int class
okay, I've gotten into class writing, and I'm taking an Int class that I wrote in Turing, and I am trying to convert it over to Ruby (I know it's reinventing the wheel, but I'm doing it just because), and some weird things are going on.

Ruby:

class Int
    def initialize(num)
        @@val = num
    end
    def add(*ints)
        ints.each do |element|
            @@val += element
        end
    end
    def subtract(*ints)
        ints.each do |element|
            @@val -= element
        end
    end
end

my_int = Int.new(6)
puts "#{my_int.add(3,4,5)}"
puts "#{my_int.subtract(3,4,5)}"


could someone please tell me why the code above would return 345 when the call to my_int.add(3,4,5) is made? It doesn't make sense why this is happening...
Author:  wtd [ Fri Nov 03, 2006 10:56 pm ]
Post subject: 
Well, one thing...

An @@ prefix indicates a class variable, rather than an instance variable.

Now, with that out of the way...

You can rewrite this:

code:
puts "#{my_int.add(3,4,5)}"
puts "#{my_int.subtract(3,4,5)}"


Much more simply as:

code:
puts my_int.add(3, 4, 5)
puts my_int.subtract(3, 4, 5)
Author:  [Gandalf] [ Sat Nov 04, 2006 11:06 pm ]
Post subject:  Re: Strange things happening in my Int class
Freakman wrote:
could someone please tell me why the code above would return 345 when the call to my_int.add(3,4,5) is made? It doesn't make sense why this is happening...

Sure it makes sense. How would " " + 3 + 4 + 5 look? Since concatenation and addition have the same precedence, it would become " 345".
Author:  wtd [ Sun Nov 05, 2006 8:27 am ]
Post subject:  Re: Strange things happening in my Int class
[Gandalf] wrote:
Freakman wrote:
could someone please tell me why the code above would return 345 when the call to my_int.add(3,4,5) is made? It doesn't make sense why this is happening...

Sure it makes sense. How would " " + 3 + 4 + 5 look? Since concatenation and addition have the same precedence, it would become " 345".


Ruby is strongly typed, so this doesn't work at all.

:


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