d-programming-language.org

[Mehrdad]

Since I didn't see this being mentioned anywhere, I thought I'd mention 
it...

On 7/4/2011 1:58 PM, Andrei Alexandrescu wrote:
> On 7/4/11 2:48 PM, bearophile wrote:
>> In this case you wrap the code in something that allows it to
>> overflow without errors, like:
>>
>> unsafe(overflows) { // code here }
>
> This approach has a number of issues. First, addressing transitivity is
> difficult. If the code in such a scope calls a function, either every
> function has two versions, or chooses one way to go about it. Each
> choice has obvious drawbacks.

C# chooses to limit the scope to the current function, and it works 
pretty well. The use is to modify the behavior of the *operators*, and 
hence, there's no transitivity issue because that's just not what it's 
used for.

> Second, programmers are notoriously bad at choosing which code is
> affecting bottom line performance, yet this feature explicitly puts the
> burden on the coder. So code will be littered with amends, yet still be
> overall slower. This feature has very poor scalability.

Actually, there is **NO** performance issue -- at least not in C#. In 
fact, if you run this program (with or without optimizations), you will 
see that they're literally the same almost all the time:

     using System;

     static class Program
     {
         static long globalVar = 0; //Make it static so it doesn't get 
optimized
         static void Main()
         {
             const long COUNT = 100000000;
             for (;;)
             {
                 var start = Environment.TickCount;
                 for (long i = 0; i < COUNT; i++)
                     checked { globalVar = i * i; }
                 System.Console.WriteLine("Checked:   {0}", 
Environment.TickCount - start);

                 start = Environment.TickCount;
                 for (long i = 0; i < COUNT; i++)
                     unchecked { globalVar = i * i; }
                 System.Console.WriteLine("Unchecked: {0}", 
Environment.TickCount - start);
             }
         }
     }

There is literally no performance issue. Ever.


Just my 2c