[#BloombergLP-bslmf-ResultType-01]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslmf.adoc[bslmf]::ResultType
:relfileprefix: ../../
:mrdocs:

Metafunction to return the result type of the specified functor type `t_FUNC`. The nested `type` is identical to `t_FUNC::result_type` if such a type exists; otherwise, it is identical to `t_FUNC::ResultType` if that type exists; otherwise, it is identical to the `t_FALLBACK` template parameter if it was specified; otherwise, it is undefined.

== Synopsis

Declared in `<bslmf_resulttype.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_FUNC,
    class t_FALLBACK = xref:BloombergLP/bslmf/Nil.adoc[bslmf::Nil],
    class = void>
struct ResultType
    : xref:BloombergLP/bslmf/ResultType_BdeIdiom-0d.adoc[ResultType_BdeIdiom<t_FUNC, t_FALLBACK>]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bslmf/ResultType_BdeIdiom-0d.adoc[ResultType_BdeIdiom<t_FUNC, t_FALLBACK>]`
| Metafunction to detect the BDE `ResultType` idiom as part of the implementation of `bslmf::ResultType`. This `struct` is instantiated when `t_FUNC::result_type` doesn't exist. This primary template is matched when `t_FUNC::ResultType` also does not exist. The `t_FALLBACK` type, if any, is produced.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslmf/ResultType_Fallback-0b/type.adoc[`type`] 
| The fallback type, unless `t_FALLBACK` is `bslmf::Nil`.
|===


== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslmf/ResultType-05.adoc[`ResultType<t_FUNC, t_FALLBACK, bsl::void_t<t_FUNC::result_type>>`] 
| Specialization of `ResultType` for when `t_FUNC::result_type` exists, i.e., when the C++ standard idiom for `result_type` is used.
|===



[.small]#Created with https://www.mrdocs.com[MrDocs]#