On 18/12/2009 16:02, retard wrote:
Fri, 18 Dec 2009 08:53:33 -0500, bearophile wrote:
Yigal Chripun:
There's a whole range of designs for this and related issues and IMO
the C++ design is by far the worst of them all.
My creativity is probably limited, so I think that while C++/D templates
have some well known problems, they are better than the strategies used
by Java, C#, Ada, Haskell, Object-C, Scala, and Delphi to define generic
code. They produce efficient code when you don't have a virtual machine
at run time, and allow to write STL-like algorithms. If you need less
performance and/or you accept worse algorithms/collections then I agree
there are designs simpler to use and cleaner than C++/D templates. If
you are able to design something better I'd like to know about your
ideas.
Templates are good for parameterizing algorithms and data structures.
They begin to have problems when they are used extensively for meta-
programming. For instance the lack of lazy evalution in the type world
forces the language to either have 'static if' or you need to add
indirection via dummy members. The language is basically purely
functional, but it's several orders of magnitude more verbose than say
Haskell.
CTFE solves some of the problems, but as a result the system becomes
really unorthogonal. Macros on the other hand solve the problem of clean
meta-programmming but are not the best way to describe generic types.
Java, C#, Scala, Haskell et al only support types as template parameters.
In addition Java erases this type info on runtime so you get even worse
performance than on C#/.NET.
To bearophile:
you're mistaken on all counts - generics (when properly implemented)
will provide the same performance as templates. Also, a VM is completely
orthogonal to this. Ada ain't VM based, is it?
to retard:
different problems should be solved with different tools. Macros should
be used for meta-programming and generics for type-parameters. they
don't exclude each other. E.g. Nemerle has an awesome macro system yet
it also has .net generics too.
As the saying goes -"when all you got is a hammer everything looks like
a nail" which is a very bad situation to be in.
templates are that hammer while a much better approach is to go and by a
toolbox with appropriate tools for your problem set.
