[Mono-dev] gmcs and The Future

[Jonathan Pryor]

On Thu, 2009-02-05 at 18:54 +0000, Marek Safar wrote:
> Here is slightly simplified version
> 
>     [Conditional("DEBUG")]
>     static void Assert (Expression<Func<bool>> e)
>     {
>         var d = e.Compile ();
>         if (!d ()) {
>             Console.WriteLine (((LambdaExpression)e).Body.ToString ());
>         }
>     }
> 
>     public static void Main ()
>     {
>         object self = null;
>         Assert (() => self != null);
>     }

Nice.  I didn't know that there was existing support already.

There's one problem, though: this prints out "(null != null)", which
isn't terribly helpful. :-)

This is one advantage to the parameter based version:

	[Conditional("DEBUG")]
	static void Assert<T>(T value, Expression<Func<T,bool>> e)
	{
		if (!d.Compile() (value))
			Console.WriteLine(
				((LambdaExpression)e).Body.ToString ());
	}

When it fails, it prints out "(v != null)" instead, which is somewhat
more useful (except that `v' won't be something the user knows about).

 - Jon