[#BloombergLP-bslmf-ResultType_BdeIdiom-0d]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslmf.adoc[bslmf]::ResultType_BdeIdiom
:relfileprefix: ../../
:mrdocs:

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.

== Synopsis

Declared in `<bslmf_resulttype.h>`

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

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bslmf/ResultType_Fallback-0b.adoc[ResultType_Fallback<t_FALLBACK>]`
| Metafunction that defines `type` to be the specified `t_FALLBACK` type unless `t_FALLBACK` is `bslmf::Nil`.
|===

== 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_BdeIdiom-00.adoc[`ResultType_BdeIdiom<t_FUNC, t_FALLBACK, bsl::void_t<t_FUNC::ResultType>>`] 
| Metafunction to detect the BDE `ResultType` idiom as part of the implementation of `bslmf::ResultType`. This specialization is instantiated by `ResultType` only if `t_FUNC::result_type` does not exist and `t_FUNC::ResultType` does exist.
|===


== Derived Classes

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslmf/ResultType-01.adoc[`ResultType`] 
| 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.
|===


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