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In computer science, generics are a technique that allows one value to take different datatype (so-called polymorphism) as long as certain contracts (so-called subtype) are kept. The programming style with it is called "generic programming".
Among OOP languages, C++, Beta, Eiffel, Ada, and later versions of Java provides generic facility. In C++, templates support generics and popularized the notion of generics.
For example, in C++ code,
templateT max (T x, T y) { if (x < y) return y; else return x;}
In this case, a pseudo-datatype T is called "subtype". T can be anything that can be compared. Most languages can deduce the actual datatype when the template is used:
max(4, 10) // implicit int
Anyway, it can also be explicit:
maxIn the later example C++ requires the explicit datatype, since the first parameter type is different from the second, and the actual T would be ambiguous.(4.3, 2)
Uncommon, template metaprogramming is a way of making algorithms evaluate when your code is compiled.
See also Partial evaluation
