Concepts

Work-in-progress.

NestedContainer

A NestedContainer is a Container that can store sequences of elements and ordered sequences.

Types
`Name`	`Type`	`Notes`
`array_type`		SequenceContainer.
`map_type`		AssociativeContainer.
`pair_type`

A NestedContainer must keep track of whether the stored type is value_type, array_type, or map_type. The semantics of insertion and erasure depends on the stored type.

Singular Semantics
`Expression`	`Return type`	`Singular semantics`	`Conditions`
`a.clear()`	`void`	Assigns value-initialized `T` to `a`.	Effects: `*a == T{}`
`a.erase(p)`	`iterator`	No effect.	Returns: Iterator `p`.
`a.erase(i, j)`	`iterator`	No effect.	Returns: Iterator `i`.
`a.insert(t)`	`iterator`	Fails.
`a.insert(i, j)`	`void`	Fails.
`a.insert(p, t)`	`iterator`	Fails.
`a.insert(p, i, j)`	`void`	Fails.

Sequence Semantics
`Expression`	`Return type`	`Sequence semantics`	`Conditions`
`a.clear()`	`void`	Removes all nested elements.	Effects: `a.empty() == true`
`a.erase(p)`	`iterator`	Removes a given element.	Requires: `T` shall be `MoveAssignable`. Effects: Erases the element pointed to by `p`. Returns: Iterator pointing to the element immediately following `p` prior to the element being erased, or `a.end()` if no such element exists.
`a.erase(i, j)`	`iterator`	Removes all elements in range.	Requires: `T` shall be `MoveAssignable`. Effects: Erases the elements in the range [`i`, j``).` `Returns:` Iterator pointing to the element pointed to by `j prior to the element being erased, or `a.end()` if no such element exists.
`a.insert(t)`	`iterator`	Inserts element at end.	Requires: `T` shall be `CopyInsertable` into `a`. Effects: `a.insert(a.end(), t)` Returns: Iterator `a.end()`
`a.insert(i, j)`	`void`	Inserts all elements in range at end.	Requires: `T` shall be `EmplaceConstructible` into `a` from `i`. `i` and `j` are not iterators into `a`. Effects:* `a.insert(a.end(), i, j)`
`a.insert(p, t)`	`iterator`	Inserts element before position.	Requires: `T` shall be `CopyInsertable` into `a`. `p` is iterator into `a`. Effects: Inserts a copy of `t` before position `p`. Returns: Iterator `p`.
`a.insert(p, i, j)`	`void`	Inserts all elements in range before position.	Requires: `T` shall be `EmplaceConstructible` into `a` from `i`. `p` is iterator into `a`. `i` and `j` are not iterators into `a`. Effects:* Inserts a copy of each element in the range [`i`, j`) into `a before position `p`.

Associative Semantics
`Expression`	`Return type`	`Associative semantics`	`Conditions`
`a.clear()`	`void`	Removes all nested elements.	Effects: `a.empty() == true`
`a.erase(p)`	`iterator`	Removes a given element.	Effects: Erases the element pointed to by `p`. Returns: Iterator pointing to the element immediately following `p` prior to the element being erased, or `a.end()` if no such element exists.
`a.erase(i, j)`	`iterator`	Removes all elements in range.	Effects: Erases the elements in the range [`i`, j``).` `Returns:` Iterator pointing to the element pointed to by `j prior to the element being erased, or `a.end()` if no such element exists.
`a.insert(t)`	`iterator`	Inserts `t`.	Requires: `T` is a `pair_type`. Effects: ` p = std::find(a.begin(), a.end(), get<0>(t)) a.insert(p, t)`
`a.insert(i, j)`	`void`	Inserts all elements in range [`i`, `j`)	Requires: Each elements in range [`i`, j`) is a `pair_type.
`a.insert(p, t)`	`iterator`	Inserts `t` with position `p` as hint.	Requires: `T` is a `pair_type`.
`a.insert(p, i, j)`	`void`	Inserts all elements in range [`i`, j`) with position `p as hint.	Requires: Each elements in range [`i`, j`) is a `pair_type.

DynamicContainer

A DynamicContainer is a NestedContainer that can also store heterogenous elements, one of which is a nullable element indicating the absence of a value.

Nullable Semantics
`Expression`	`Return type`	`Nullable semantics`	`Conditions`
`a.clear()`	`void`	No effect.
`a.erase(p)`	`iterator`	No effect.	Returns: Iterator `p`.
`a.erase(i, j)`	`iterator`	No effect.	Returns: Iterator `i`.
`a.insert(t)`	`iterator`	Changes stored type to SequenceContainer and inserts element.	Requires: `T` shall be `CopyInsertable` into `a`. Effects: `a` becomes a sequenced array containing a copy of `t`. Returns: Iterator `a.end()`.
`a.insert(i, j)`	`void`	Changes stored type to SequenceContainer and inserts all elements in range.	Requires: `T` shall be `EmplaceConstructible` into `a`. Effects: `a` becomes a sequenced array containing a copy of each element in the range [`i`, `j`).
`a.insert(p, t)`	`iterator`	Fails.
`a.insert(p, i, j)`	`void`	Fails.