[#BloombergLP-bslstl-Function_IsInvocableWithPrototype-06]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::Function_IsInvocableWithPrototype
:relfileprefix: ../../
:mrdocs:

Forward declaration of the invocability metafunction for `bsl::function`.

== Synopsis

Declared in `<bslstl_function.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class PROTOTYPE,
    class FUNC>
struct Function_IsInvocableWithPrototype;
----

== Description

Forward declaration of the component‐private `Function_IsInvocableWithPrototype` `struct` template. The primary (unspecialized) template is not defined. This `struct` template implements a boolean metafunction that publicly inherits from `bsl::true_type` if an object of the specified `FUNC` type is invocable under the specified `PROTOTYPE`, and inherits from `bsl::false_type` otherwise. An object of `FUNC` type is invocable under the `PROTOTYPE` if it is Lvalue‐Callable with the arguments of the `PROTOTYPE`, and returns an object of type convertible to the return type of the `PROTOTYPE`. If the return type of the `PROTOTYPE` is `void`, then any type is considered convertible to the return type of the `PROTOTYPE`. In C++03, `FUNC` is considered Lvalue‐Callable with the argument and return types of the `PROTOTYPE` if it is not an integral type. This `struct` template requires `PROTOTYPE` to be an unqualified function type.

== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslstl/Function_IsInvocableWithPrototype-00.adoc[`Function_IsInvocableWithPrototype<RET(ARGS...), FUNC>`] 
| Boolean metafunction reporting whether `FUNC` can initialize `bsl::function`.
|===



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