[#llvm-concat_iterator]
= xref:llvm.adoc[llvm]::concat_iterator
:relfileprefix: ../
:mrdocs:

Iterator wrapper that concatenates sequences together.

== Synopsis

Declared in `<llvm/ADT/STLExtras.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename ValueT,
    typename... IterTs>
class concat_iterator
    : public xref:llvm/iterator_facade_base-08c.adoc[iterator_facade_base<concat_iterator<ValueT, IterTs...>, std::forward_iterator_tag, ValueT>]
----

== Description

This can concatenate different iterators, even with different types, into a single iterator provided the value types of all the concatenated iterators expose `reference` and `pointer` types that can be converted to `ValueT &` and `ValueT *` respectively. It doesn't support more interesting/customized pointer or reference types.

Currently this only supports forward or higher iterator categories as inputs and always exposes a forward iterator interface.

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:llvm/iterator_facade_base-08c.adoc[iterator_facade_base<concat_iterator<ValueT, IterTs...>, std::forward_iterator_tag, ValueT>]`
| CRTP base class which implements the entire standard iterator facade in terms of a minimal subset of the interface.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:llvm/iterator_facade_base-08c/difference_type.adoc[`difference_type`] 
| Signed type used to express the distance between iterators.
| xref:llvm/iterator_facade_base-08c/iterator_category.adoc[`iterator_category`] 
| Iterator category tag for this facade.
| xref:llvm/iterator_facade_base-08c/pointer.adoc[`pointer`] 
| Pointer type returned by the iterator.
| xref:llvm/iterator_facade_base-08c/reference.adoc[`reference`] 
| Reference type returned by the iterator.
| xref:llvm/iterator_facade_base-08c/value_type.adoc[`value_type`] 
| Value type produced by the iterator.
|===


== Enums

[cols="1,4"]
|===
| Name| Description
| xref:llvm/iterator_facade_base-08c/_04enum.adoc[`Unnamed enum`] 
| Capability flags for the iterator category.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:llvm/concat_iterator/2constructor.adoc[`concat_iterator`]         [.small]#[constructor]#
| Construct an iterator from a sequence of ranges.
| xref:llvm/concat_iterator/operator_star.adoc[`operator*`] 
| Return a reference to the current concatenated element.
| xref:llvm/iterator_facade_base-08c/operator_plus.adoc[`operator+`] 
| Advance the iterator by `n` and return the result.
| xref:llvm/concat_iterator/operator_inc-0d.adoc[`operator++`] 
| Increment operators
| xref:llvm/iterator_facade_base-08c/operator_minus.adoc[`operator‐`] 
| Retreat the iterator by `n` and return the result.
| xref:llvm/iterator_facade_base-08c/operator_dec-02.adoc[`operator‐‐`] 
| Decrement operators
| xref:llvm/iterator_facade_base-08c/operator_ptr.adoc[`operator‐>`] 
| Return a proxy pointer to the current element.
| xref:llvm/iterator_facade_base-08c/operator_subs.adoc[`operator[]`] 
| Return a proxy to the element at offset `n.`
| xref:llvm/concat_iterator/operator_eq.adoc[`operator==`] 
| Return true if both iterators are at the same concatenated position.
| xref:llvm/iterator_facade_base-08c/operator_le.adoc[`operator<=`] 
| Return true if this iterator is less than or equal to `RHS.`
| xref:llvm/iterator_facade_base-08c/operator_gt.adoc[`operator>`] 
| Return true if this iterator is greater than `RHS.`
| xref:llvm/iterator_facade_base-08c/operator_ge.adoc[`operator>=`] 
| Return true if this iterator is greater than or equal to `RHS.`
|===


== Using Declarations

[cols="1,4"]
|===
| Name| Description
| xref:llvm/concat_iterator/operator++.adoc[`operator++`] 
| Bring the postfix increment operator into scope.
|===


== Protected Types

[cols="1,4"]
|===
| Name| Description
| xref:llvm/iterator_facade_base-08c/PointerProxy.adoc[`PointerProxy`] 
| Proxy that yields a pointer from a copied reference.
| xref:llvm/iterator_facade_base-08c/ReferenceProxy.adoc[`ReferenceProxy`] 
| Proxy that yields a reference from a copied iterator.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:llvm/operator_plus-040.adoc[`operator+`]
| Return an iterator `n` positions after `i.`
|===


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