A page that documents a concept has the following sections.

• Summary: a description of the concept's purpose.

• Refinement of: a list of other concepts that this concept refines , with links to those concepts.

• Associated types: a concept is a set of requirements on some type. Frequently, however, some of those requirements involve some other type. For example, one of the Unary Function requirements is that a Unary Function must have an argument type ; if F is a type that models Unary Function and f is an object of type F, then, in the expression f(x), x must be of F 's argument type. If a concept does have any such associated types, then they are defined in this section.

• Notation: the next three sections, definitions, valid expressions, and expression semantics, present expressions involving types that model the concept being defined. This section defines the meaning of the variables and identifiers used in those expressions.

• Definitions: some concepts, such as LessThan Comparable, use specialized terminology. If a concept requires any such terminology, it is defined in this section.

• Valid Expressions: a type that models a concept is required to support certain operations. In most cases, it doesn't make sense to describe this in terms of specific functions or member functions: it doesn't make any difference, for example, whether a type that models Input Iterator uses a global function or a member function to provide operator++. This section lists the expressions that a type modeling this concept must support. It includes any special requirements (if any) on the types of the expression's operands, and the expression's return type (if any).

• Expression Semantics: the previous section, valid expressions, lists which expressions involving a type must be supported; it doesn't, however, define the meaning of those expressions. This section does: it lists the semantics, preconditions, and postconditions for the expressions defined in the previous section.

• Complexity Guarantees: in some cases, the run-time complexity of certain operations is an important part of a concept's requirements. For example, one of the most significant distinctions between a Bidirectional Iterator and a Random Access Iterator is that, for random access iterators, expressions like p + n take constant time. Any such requirements on run-time complexity are listed in this section.

• Invariants: many concepts require that some property is always true for objects of a type that models the concept being defined. For example, LessThan Comparable imposes the requirement of transitivity : if x < y and y < z, then x < z. Some such properties are "axioms" (that is, they are independent of any other requirements) and some are "theorems" (that is, they follow either from requirements in the expression semantics section or from other requirements in the invariants section).

• Models: a list of examples of types that are models of this concept. Note that this list is not intended to be complete: in most cases a complete list would be impossible, because there are an infinite number of types that could model the concept.

• Notes: footnotes (if any) that are referred to by other parts of the page.

• See Also: links to other related pages.