Concepts

A concept is a predicate that defines requirements on template arguments. Concepts are used within the constraints of a template declaration to a) express the kinds of types that can be used with that template and b) to enforce those requirements at compile time.

Each concept defines its requirements in terms of syntax or use patterns and the required behavior of those operations.

The primary groups of concepts are:

• Language concepts – These concepts describe the kinds of types defined by the C++ Programming Language. These primarily characterize types by their “shape” or category rather than their uses.

• Value concepts – Requirements for the initialization of objects, copying and moving, and comparison. These establish the abstract notion of “value” (as in value semantics) in modern C++.

• Function concepts – These concepts describe requirements on function arguments.

• Iterator concepts – Requirements for iterators. An iterator is an abstraction of a position within a linear sequence.

• Range concepts – Requirements for ranges. A range denotes the beginning and the end of a sequence.

• Stream concepts – Requirements for stream abstractions, including formatted I/O streams.