[#bsl-function-0a]
= xref:bsl.adoc[bsl]::function
:relfileprefix: ../
:mrdocs:

Forward declaration.

== Synopsis

Declared in `<bslstl_function.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class PROTOTYPE>
class function
    : public xref:BloombergLP/bslstl/Function_Variadic-0e.adoc[BloombergLP::bslstl::Function_Variadic<PROTOTYPE>]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bslstl/Function_Variadic-0e.adoc[BloombergLP::bslstl::Function_Variadic<PROTOTYPE>]`
| This component‐private class template contains the physical representation and provides the variadic interfaces for `bsl::function`.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/function-0a/allocator_type.adoc[`allocator_type`] 
| Alias for the allocator type of the function representation.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/function-0a/2constructor-075.adoc[`function`]         [.small]#[constructor]#
| Constructors
| xref:bsl/function-0a/operator_assign-01.adoc[`operator=`] 
| Assignment operators
| xref:bsl/function-0a/allocator.adoc[`allocator`] 
| Return `get_allocator().mechanism()`. Note that this function exists for BDE compatibility and is not part of the C++ Standard Library.
| xref:bsl/function-0a/get_allocator.adoc[`get_allocator`] 
| Return (a copy of) the allocator used to supply memory for this `function`.
| xref:bsl/function-0a/isInplace.adoc[`isInplace`] 
| Return whether this object's target uses in‐place storage.
| xref:bsl/function-0a/swap.adoc[`swap`] 
| Exchange the targets held by this `function` and the specified `other`.
| xref:bsl/function-0a/target-0a9.adoc[`target`] 
| `target` overloads
| xref:bsl/function-0a/target_type.adoc[`target_type`] 
| Return `typeid(void)` if this object is empty; otherwise `typeid(FUNC)` where `FUNC` is the type of the target object.
| xref:bsl/function-0a/2conversion-05.adoc[`operator BloombergLP::bdef_Function<PROTOTYPE*>&`] 
| Convert `*this` to a mutable `bdef_Function` reference by downcasting.
| xref:bsl/function-0a/2conversion-0d.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<function, UsesAllocatorArgT>`] 
| Nested trait declaration for `bslmf::UsesAllocatorArgT`.
| xref:bsl/function-0a/2conversion-0a.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<function, UsesBslmaAllocator>`] 
| Nested trait declaration for `bslma::UsesBslmaAllocator`.
| xref:bsl/function-0a/2conversion-07.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<function, is_nothrow_move_constructible>`] 
| Nested trait declaration for `is_nothrow_move_constructible`.
| xref:bsl/function-0a/2conversion-03.adoc[`operator bool`] 
| Return whether this `function` currently holds a target.
| xref:bsl/function-0a/2conversion-0c.adoc[`operator BloombergLP::bdef_Function<PROTOTYPE*> const&`] 
| Convert `*this` to a const `bdef_Function` reference by downcasting.
|===


== Using Declarations

[cols="1,4"]
|===
| Name| Description
| xref:bsl/function-0a/operator().adoc[`operator()`] 
| Invoke the target with the call arguments, or throw if empty.
|===


== Deduction Guides

[cols="1,4"]
|===
| Name| Description
| xref:bsl/function-00.adoc[`function<PROTOTYPE>`] 
| Deduce the template parameter `PROTOTYPE` from the signature of the `operator()` of the functor supplied to the constructor of `function`.
| xref:bsl/function-066.adoc[`function<PROTOTYPE>`] 
| Deduce the template parameter `PROTOTYPE` from the signature of the `operator()` of the functor supplied to the constructor of `function`.
| xref:bsl/function-06d.adoc[`function<RET(ARGS...)>`] 
| Deduce the template parameter `PROTOTYPE` from the signature of the function supplied to the constructor of `function`.
| xref:bsl/function-05.adoc[`function<RET(ARGS...)>`] 
| Deduce the template parameter `PROTOTYPE` from the signature of the function supplied to the constructor of `function`.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/operator_not_eq-0b.adoc[`operator!=`]
| Return `true` if the specified `function` is not empty.
| xref:bsl/operator_eq-09d2.adoc[`operator==`]
| Return `true` if the specified `function` is empty.
| xref:bsl/swap-026.adoc[`swap`]
| Exchange the targets held by the specified `a` and `b` functions.
|===


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