Sunday, February 05, 2006
Type Inference in C#: No Trail Arguments Deduction
class TestAccording to the C# Version 2.0 Specification, "The presence of type inference allows a more convenient syntax to be used for calling a generic method, and allows the programmer to avoid specifying redundant type information". All so true. Unfortunately, they didn't look close enough to what C++ can do, that is, trail argument deduction.
{
private static void f< T >( T p ) { }
public static void Main()
{
// explicit type argument
f< int >( 3 ) ;
// type inference
f( 3 ) ;
}
}
This is legal C++ :
template< class T1, class T2 > void f( T2 p2 )but this is not legal C# :
{
}
int main()
{
f< double >( 3 ) ; // calls f< double, int >( 3 )
}
class TestWhy would you want trail argument deduction? For the same reasons you want type inference: to get a more convenient syntax, and to avoid specifying redundant type information. (Of course, in real cases, f would make use of type T1 inside its body; I could definitely use something like that for my GUI rules library [see my post "C#: In search of language"]).
{
private static void f< T1, T2 >( T2 p ) { }
public static void Main()
{
f< double, int >( 3 ) ; // works
f< double >( 3 ) ; // error
}
}
Overall my experience with C# is mixed. There is some good stuff in it. But as soon as you try to do something slightly more advanced, you're hitting a wall. It's so disappointing. Gotta do something about it :-)).
