🚀 go-pugleaf

Generics in C#, Java, and C++
A Conversation with Anders Hejlsberg, Part VII
by Bill Venners with Bruce Eckel
January 26, 2004

http://www.artima.com/intv/generics.html

"Comparing C# Generics to C++ Templates
Bruce Eckel: How do C# generics compare with C++ templates? 

Anders Hejlsberg: To me the best way to understand the distinction
between C# generics and C++ templates is this: C# generics are
really just like classes, except they have a type parameter. C++
templates are really just like macros, except they look like
classes. 

The big difference between C# generics and C++ templates shows up in
when the type checking occurs and how the instantiation occurs.
First of all, C# does the instantiation at runtime. C++ does it at
compile time, or perhaps at link time. But regardless, the
instantiation happens in C++ before the program runs. That's
difference number one. Difference number two is C# does strong type
checking when you compile the generic type. For an unconstrained
type parameter, like List<T>, the only methods available on values
of type T are those that are found on type Object, because those are
the only methods we can generally guarantee will exist. So in C#
generics, we guarantee that any operation you do on a type parameter
will succeed. 

C++ is the opposite. In C++, you can do anything you damn well
please on a variable of a type parameter type. But then once you
instantiate it, it may not work, and you'll get some cryptic error
messages. For example, if you have a type parameter T, and variables
x and y of type T, and you say x + y, well you had better have an
operator+ defined for + of two Ts, or you'll get some cryptic error
message. So in a sense, C++ templates are actually untyped, or
loosely typed. Whereas C# generics are strongly typed...."

Oczywiscie, zeby upzredic ewentualne komantarze, zgadzam sie ze
autorzy sa niekompetentni i niechetnei nastawieni do C++. C++ jest
po prostu dla nich za trudny. Zwlaszcza "Modern C++"

A.L.