// bslmf_ispointer.h                                                  -*-C++-*-
#ifndef INCLUDED_BSLMF_ISPOINTER
#define INCLUDED_BSLMF_ISPOINTER

#include <bsls_ident.h>
BSLS_IDENT("$Id: $")

//@PURPOSE: Provide a compile-time check for pointer types.
//
//@CLASSES:
//  bsl::is_pointer: standard meta-function for determining pointer types
//  bsl::is_pointer_v: the result value of the `bsl::is_pointer` meta-function
//  bsl::IsPointer: meta-function for determining pointer types
//
//@SEE_ALSO: bslmf_integralconstant
//
//@DESCRIPTION: This component defines two meta-functions, `bsl::is_pointer`
// and `BloombergLP::bslmf::IsPointer` and a template variable
// `bsl::is_pointer_v`, that represents the result value of the
// `bsl::is_pointer` meta-function.  All these meta-functions may be used to
// query whether or not a type is a pointer type.
//
// `bsl::is_pointer` meets the requirements of the `is_pointer` template
// defined in the C++11 standard [meta.unary.cat], while `bslmf::IsPointer` was
// devised before `is_pointer` was standardized.
//
// The two meta-functions are functionally equivalent.  The major difference
// between them is that the result for `bsl::is_pointer` is indicated by the
// class member `value`, while the result for `bslmf::IsPointer` is indicated
// by the class member `value`.
//
// Note that `bsl::is_pointer` should be preferred over `bslmf::IsPointer`, and
// in general, should be used by new components.
//
// Also note that the template variable `is_pointer_v` is defined in the C++17
// standard as an inline variable.  If the current compiler supports the inline
// variable C++17 compiler feature, `bsl::is_pointer_v` is defined as an
// `inline constexpr bool` variable.  Otherwise, if the compiler supports the
// variable templates C++14 compiler feature, `bsl::is_pointer_v` is
// defined as a non-inline `constexpr bool` variable.  See
// `BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES` and
// `BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES` macros in
// bsls_compilerfeatures component for details.
//
///Usage
///-----
// In this section we show intended use of this component.
//
///Example 1: Verify Pointer Types
///- - - - - - - - - - - - - - - -
// Suppose that we want to assert whether a particular type is a pointer type.
//
// First, we create two `typedef`s -- a pointer type and a non-pointer type:
// ```
// typedef int  MyType;
// typedef int *MyPtrType;
// ```
// Now, we instantiate the `bsl::is_pointer` template for each of the
// `typedef`s and assert the `value` static data member of each instantiation:
// ```
// assert(false == bsl::is_pointer<MyType>::value);
// assert(true  == bsl::is_pointer<MyPtrType>::value);
// ```
// Note that if the current compiler supports the variable templates C++14
// feature then we can re-write the snippet of code above using the
// `bsl::is_pointer_v` variable as follows:
// ```
// #ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
//   assert(false == bsl::is_pointer_v<MyType>);
//   assert(true  == bsl::is_pointer_v<MyPtrType>);
// #endif
// ```

#include <bslscm_version.h>

#include <bslmf_integralconstant.h>

#include <bsls_compilerfeatures.h>
#include <bsls_keyword.h>
#include <bsls_platform.h>

#ifndef BDE_DONT_ALLOW_TRANSITIVE_INCLUDES
#include <bslmf_removecv.h>
#endif // BDE_DONT_ALLOW_TRANSITIVE_INCLUDES

namespace bsl {

                         // =================
                         // struct is_pointer
                         // =================

/// This `struct` template implements the `is_pointer` meta-function defined
/// in the C++11 standard [meta.unary.cat] to determine if the (template
/// parameter) `t_TYPE` is a pointer.  This `struct` derives from
/// `bsl::true_type` if the `t_TYPE` is a pointer type (but not a
/// pointer-to-non-static-member type), and `bsl::false_type` otherwise.
template <class t_TYPE>
struct is_pointer : bsl::false_type {
};

/// This partial specialization of `is_pointer` derives from
/// `bsl::true_type` for when the (template parameter) `t_TYPE` is a
/// (cv-unqalified) pointer type.
template <class t_TYPE>
struct is_pointer<t_TYPE *> : bsl::true_type {
};

// Preferred implementation avoids a second dispatch for arbitrary cv-qualified
// types.

/// This partial specialization of `is_pointer` derives from
/// `bsl::true_type` for when the (template parameter) `t_TYPE` is a `const`
/// qualified pointer type.
template <class t_TYPE>
struct is_pointer<t_TYPE *const> : bsl::true_type {
};

/// This partial specialization of `is_pointer` derives from
/// `bsl::true_type` for when the (template parameter) `t_TYPE` is a
/// `volatile` qualified pointer type.
template <class t_TYPE>
struct is_pointer<t_TYPE *volatile> : bsl::true_type {
};

/// This partial specialization of `is_pointer` derives from
/// `bsl::true_type` for when the (template parameter) `t_TYPE` is a 'const
/// volatile' qualified pointer type.
template <class t_TYPE>
struct is_pointer<t_TYPE *const volatile> : bsl::true_type {
};

#ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
/// This template variable represents the result value of the
/// `bsl::is_pointer` meta-function.
template <class t_TYPE>
BSLS_KEYWORD_INLINE_VARIABLE constexpr bool is_pointer_v =
                                                     is_pointer<t_TYPE>::value;
#endif

}  // close namespace bsl

namespace BloombergLP {
namespace bslmf {

                         // ================
                         // struct IsPointer
                         // ================

/// This `struct` template implements a meta-function to determine if the
/// (template parameter) `t_TYPE` is a pointer type.  This `struct` derives
/// from `bsl::true_type` if the `t_TYPE` is a pointer type (but not a
/// pointer to non-static member), and `bsl::false_type` otherwise.
///
/// Note that this `struct` is functionally equivalent to `bsl::is_pointer`,
/// and the use of `bsl::is_pointer` should be preferred.
template <class t_TYPE>
struct IsPointer : bsl::is_pointer<t_TYPE>::type {
};

}  // close package namespace
}  // close enterprise namespace

#ifndef BDE_OPENSOURCE_PUBLICATION  // BACKWARD_COMPATIBILITY
// ============================================================================
//                           BACKWARD-COMPATIBILITY
// ============================================================================

#ifdef bslmf_IsPointer
#undef bslmf_IsPointer
#endif

/// This alias is defined for backward-compatibility.
#define bslmf_IsPointer bslmf::IsPointer
#endif  // BDE_OPENSOURCE_PUBLICATION -- BACKWARD_COMPATIBILITY

#endif

// ----------------------------------------------------------------------------
// Copyright 2013 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
