Question

Consider this

        int i = 2147483647;
        var n = i + 3;
        i = n;

        Console.WriteLine(i);           // prints -2147483646    (1)
        Console.WriteLine(n);           // prints -2147483646    (2)
        Console.WriteLine(n.GetType()); // prints System.Int32   (3)

I am confused with following

• (1) how could int hold the value -2147483646 ? (int range = -2,147,483,648 to 2,147,483,647)
• (2) why does this print -2147483648 but not 2147483648 (compiler should
  decide better type as int range
  exceeds)
• (3) if it is converted somewhere, why n.GetType() gives System.Int32
  ?

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Edit1: Made the correction: Now you will get What I am Getting. (sorry for that)

var n = i + 1; to

var n = i + 3;

Edit2: One more thing, if it as overflow, why is an exception not raised ?

Addition: as the overflow occurs, is it not right to set the type for

var n

in statement var n = i + 3; to another type accordingly ?

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you are welcome to suggest a better title, as this is not making sense to…. me at least

Thanks

Answer 1

Update: Poster fixed his question.

1) This is output is expected because you added 3 to int.MaxValue causing an overflow. In .NET by default this is a legal operation in unchecked code giving a wrap-around to negative values, but if you add a checked block around the code it will throw an OverflowException instead.

2) The type of a variable declared with var is determined at compile time not runtime. It’s a rule that adding two Int32s gives an Int32, not a UInt32, an Int64 or something else. So even though at runtime you can see that the result is too big for an Int32, it still has to return an Int32.

3) It’s not converted to another type.