# Writable Iterator Concept

A class or built-in type `X` models the Writable Iterator concept if, in addition to `X` being Copy Constructible, the following expressions are valid and respect the stated semantics. Writable Iterators have an associated set of value types.

Writable Iterator Requirements (in addition to Copy Constructible)
Expression | Return Type | Precondition
--- | --- | ---
`*a = o` |  | pre: The type of `o` is in the set of value types of `X`