[#BloombergLP-bslma-AAModelIsSupported-06]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslma.adoc[bslma]::AAModelIsSupported
:relfileprefix: ../../
:mrdocs:

Predicate metafunction that determines if the specified `TYPE` supports the specified `MODEL` AA model. It yields (i.e., is derived from) `bsl:true_type` if type `TYPE` supports AA model `MODEL`; otherwise it yields `false_type`. `MODEL` Must be one of `AAModelNone`, `AAModelLegacy`, `AAModelBsl`, `AAModelPmr`, or `AAModelStl`. This metafunction can yield `true_type` for more than one type `MODEL` type, e.g., it will yield `true_type` if `TYPE` is *bsl‐AA*, and `MODEL` is either `AAModelBsl` or `AAModelLegacy`, since `TYPE` can be constructed with either allocator type.

== Synopsis

Declared in `<bslma_aamodel.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class TYPE,
    class MODEL>
struct AAModelIsSupported
    : xref:bsl/false_type.adoc[bsl::false_type]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:bsl/false_type.adoc[bsl::false_type]`
| Metafunction representing the boolean constant `false`.
|===

== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/AAModelIsSupported-01a.adoc[`AAModelIsSupported<TYPE, AAModelBsl>`] 
| Specialization of `AAModelIsSupported` for `MODEL == AAModelBsl`, yielding `true_type` if `TYPE::allocator_type` exists and is convertible from `bsl::allocator<char>`.
| xref:BloombergLP/bslma/AAModelIsSupported-00.adoc[`AAModelIsSupported<TYPE, AAModelLegacy>`] 
| Specialization of `AAModelIsSupported` for `MODEL == AAModelStl`, yielding `true_type` if `TYPE` can use `bslma::Allocator *` as its memory resource. Specifically, it is true if `UsesBslmaAllocator<TYPE>` is true or if `TYPE::allocator_type` exists and is convertible from `bslma::Allocator *`.
| xref:BloombergLP/bslma/AAModelIsSupported-04.adoc[`AAModelIsSupported<TYPE, AAModelNone>`] 
| Specialization of `AAModelIsSupported` for `MODEL == AAModelNone`, always yielding `true_type`.
| xref:BloombergLP/bslma/AAModelIsSupported-0c.adoc[`AAModelIsSupported<TYPE, AAModelPmr>`] 
| Specialization of `AAModelIsSupported` for `MODEL == AAModelPmr`, yielding `true_type` if `TYPE::allocator_type` exists and is convertible from `bsl::polymorphic_allocator<char>`.
| xref:BloombergLP/bslma/AAModelIsSupported-01d.adoc[`AAModelIsSupported<TYPE, AAModelStl>`] 
| Specialization of `AAModelIsSupported` for `MODEL == AAModelStl`, yielding `true_type` if `TYPE::allocator_type` exists; otherwise, yielding `false_type` unless `AAModelIsSupported<TYPE, AAModelBsl>` is true. The latter condition exists so that *bsl‐AA* always implies *stl‐AA* even if `AAModelIsSupported<TYPE, AAModelBsl>` is explicitly specialized to true for a type that does not have an `allocator_type` member.
|===



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