RE: Generics in .NET 2.0 SUCK

From: Beeeeeeeeeeeeves (Beeeeeeeeeeeeves_at_discussions.microsoft.com)
Date: 07/27/04 

Date: Tue, 27 Jul 2004 10:05:40 -0700

The reason Generics in .NET 2.0 SUCK ?
Likely because they are a complete crib off templates in C++, which ALSO SUCK!!!
They are the most POOR idea for a way of programming I have ever seen.

"Ruediger Klaehn" wrote:

> Sorry about the harsh language, but I have to vent my anger to somebody who
> actually understands what I am talking about. Complaining to my girlfriend
> is not going to produce any meaningful results other than straining our
> relationship...
>
> I just downloaded Visual C# Express Edition to mess with .NET 2.0 generics.
> Being a numerically inclined developer, the first thing I wanted to write
> was a generic complex number class. I also have some quite large vector and
> matrix libraries that I would love to convert to use generics.
>
> Imagine my surprise when I found out that what I want is basically
> impossible. I want a complex number class that can work with any basic data
> type like so: complex<float>, complex<double>, complex<decimal> and so on.
> This is something that is done very often in C++ and one of the main
> applications of generics there.
>
> This was my first try (this is only an excerpt):
>
> struct complex<T>
> {
> public T re,im;
> complex<T>(T re,T im)
> {
> this.re=re;this.im=im;
> }
> complex<T> Sum(complex<T> a,complex<T> b)
> {
> return new complex<T>(a.re+b.re,a.im+b.im);
> }
> }
>
> Something like this would work in C++, since it does not have constraints on
> type parameters. But in .NET, when you specify a type parameter without
> constraints it is assumed to be a System.Object, which of course does not
> have a + operator.
>
> So I thought, probably there is a way to specify a method constraint for T
> such that T must have a certain (static) method or a certain operator
> method. But the only thing like this is the new() constraint to specify
> that a class must have a default constructor.
>
> My second thought was that there might be some interface like IArithmetic.
> This is of course complicated by the fact that interfaces can not contain
> static methods. But something like
>
> interface IArithmetic<T> {
> void Add(T a);
> void Subtract(T a);
> void Multiply(T a);
> void Divide(T a);
> }
>
> should do the trick. This would not be very elegant, but quite sufficient.
> Given that there is an interface called IComparable<T> this should not be
> too much to ask. Maybe there should even be something more granular like
>
> interface IAddable<T> {
> void Add(T a);
> }
>
> ....
>
> interface
> IArithmetic<T>:IAddable<T>,ISubtractable<T>,IMultipliable<T>,IDivisible<T>
> {
> }
>
> or something. This solution would be similar to the approach taken with
> IComparable and IComparable<T>.
>
> But no such interface exists in the System namespace. So I would have to
> wrap all the basic data types into structs that actually implement this
> interface, like so:
>
> struct ArithmeticInt : IArithmetic<int> {
> private int value;
> ...
> }
>
> struct ArithmeticDouble : IArithmetic<double> {
> private double value;
> ...
> }
>
> But this would be a lot of work and, even worse, would lead to absymal
> performance since in my experience the .NET JIT compiler is too dumb to get
> rid of the wrapper code.
>
> There are of course some workarounds like having a separate type parameter
> for the operations, like this:
>
> struct Complex<T,Ops> where Ops:IArithmeticOps<T>
> {
> ...
> }
>
> But this yields inacceptable performance.
>
> What is really required is a way to specify *method* *constraints* instead
> of just interface constraints and the new() constraint.
>
> Another option would be to allow static methods in interfaces and to provide
> an IArithmethic interface in the System namespace, but I would prefer the
> first option.
>
> Without something like this, generics are only good for typed collections.
> Adding so much new syntax and complexity just to make collections faster
> and more type safe seems like a waste of time!
>

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