[#BloombergLP-bdlb-TransformIterator_Traits-0f]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::TransformIterator_Traits
:relfileprefix: ../../
:mrdocs:

This component‐private class defines various types that are used in the implementation of the transform iterator.

== Synopsis

Declared in `<bdlb_transformiterator.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class FUNCTOR,
    class ITERATOR>
struct TransformIterator_Traits;
----

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlb/TransformIterator_Traits-0f/BaseIteratorTraits.adoc[`BaseIteratorTraits`] 
| Define the iterator traits class of the underlying iterator.
| xref:BloombergLP/bdlb/TransformIterator_Traits-0f/ResultType.adoc[`ResultType`] 
| Define the result type returned by the functor. This is not necessarily the same type as the dereference of the iterator. In C++11, the result type can be determined automatically. Note that various iterations of the language standard might want to instead use `std::result_of` or `std::invoke_result` (which have been variously added and then deprecated), but the following works from C++11 onwards.
| xref:BloombergLP/bdlb/TransformIterator_Traits-0f/difference_type.adoc[`difference_type`] 
| Type used to represent distances between iterators.
| xref:BloombergLP/bdlb/TransformIterator_Traits-0f/iterator_category.adoc[`iterator_category`] 
| Define the iterator category of the transform iterator. If the functor returns a reference type, we pass through the iterator category of the underlying iterator, otherwise we use the input iterator tag (because all the other tags require that dereferencing produces a reference).
| xref:BloombergLP/bdlb/TransformIterator_Traits-0f/pointer.adoc[`pointer`] 
| 
| xref:BloombergLP/bdlb/TransformIterator_Traits-0f/reference.adoc[`reference`] 
| Define the remaining standard types of the transform iterator.
| xref:BloombergLP/bdlb/TransformIterator_Traits-0f/value_type.adoc[`value_type`] 
| Value type produced by applying the functor to a dereferenced underlying iterator.
|===


== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlb/TransformIterator_Traits-05.adoc[`TransformIterator_Traits<RESULT(*)(ARGUMENT), ITERATOR>`] 
| Specialize the transform iterator traits template for functors that are function or function pointer types. It is sufficient to inherit from the version of the traits class that corresponds to a `bsl::function` of the function type parameter.
| xref:BloombergLP/bdlb/TransformIterator_Traits-04.adoc[`TransformIterator_Traits<RESULT(ARGUMENT), ITERATOR>`] 
| 
|===


== Derived Classes

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlb/TransformIterator_Traits-04.adoc[`TransformIterator_Traits<RESULT(ARGUMENT), ITERATOR>`] 
| 
| xref:BloombergLP/bdlb/TransformIterator_Traits-05.adoc[`TransformIterator_Traits<RESULT(*)(ARGUMENT), ITERATOR>`] 
| Specialize the transform iterator traits template for functors that are function or function pointer types. It is sufficient to inherit from the version of the traits class that corresponds to a `bsl::function` of the function type parameter.
|===


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