Program Listing for File symengine_casts.h¶
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#ifndef SYMENGINE_CASTS_H
#define SYMENGINE_CASTS_H
#include <iostream>
#include <limits>
#include <symengine/symengine_config.h>
#include <symengine/symengine_assert.h>
namespace SymEngine
{
// Reference modifications.
template <typename T>
struct remove_reference {
typedef T type;
};
template <typename T>
struct remove_reference<T &> {
typedef T type;
};
// Use implicit_cast as a safe version of static_cast or const_cast
// for upcasting in the type hierarchy (i.e. casting a pointer to Foo
// to a pointer to SuperclassOfFoo or casting a pointer to Foo to
// a const pointer to Foo).
// When you use implicit_cast, the compiler checks that the cast is safe.
// Such explicit implicit_casts are necessary in surprisingly many
// situations where C++ demands an exact type match instead of an
// argument type convertable to a target type.
//
// The From type can be inferred, so the preferred syntax for using
// implicit_cast is the same as for static_cast etc.:
//
// implicit_cast<ToType>(expr)
template <typename To, typename From>
inline To implicit_cast(const From &f)
{
return f;
}
// When you upcast (that is, cast a pointer from type Foo to type
// SuperclassOfFoo), it's fine to use implicit_cast<>, since upcasts
// always succeed. When you downcast (that is, cast a pointer from
// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because
// how do you know the pointer is really of type SubclassOfFoo? It
// could be a bare Foo, or of type DifferentSubclassOfFoo. Thus,
// when you downcast, you should use this macro. In debug mode, we
// use dynamic_cast<> to double-check the downcast is legal (we die
// if it's not). In normal mode, we do the efficient static_cast<>
// instead. Thus, it's important to test in debug mode to make sure
// the cast is legal!
// This is the only place in the code we should use dynamic_cast<>.
// In particular, you SHOULDN'T be using dynamic_cast<> in order to
// do RTTI (eg code like this:
// if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo);
// if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo);
// You should design the code some other way not to need this.
template <typename To, typename From> // use like this: down_cast<T*>(foo).
inline To down_cast(From *f) // Only accept pointers.
{
// Ensures that To is a sub-type of From *. This test is here only
// for compile-time type checking, and has no overhead in an
// optimized build at run-time, as it will be optimized away
// completely.
if (false) {
implicit_cast<From *, To>(0);
}
SYMENGINE_ASSERT(f == NULL || dynamic_cast<To>(f) != NULL);
return static_cast<To>(f);
}
template <typename To, typename From> // use like this: down_cast<T&>(foo);
inline To down_cast(From &f)
{
typedef typename remove_reference<To>::type *ToAsPointer;
// Ensures that To is a sub-type of From *. This test is here only
// for compile-time type checking, and has no overhead in an
// optimized build at run-time, as it will be optimized away
// completely.
if (false) {
implicit_cast<From *, ToAsPointer>(0);
}
SYMENGINE_ASSERT(dynamic_cast<ToAsPointer>(&f) != NULL);
return *static_cast<ToAsPointer>(&f);
}
template <typename To, typename From>
inline To
numeric_cast(From f,
typename std::enable_if<(std::is_signed<From>::value
&& std::is_signed<To>::value)
|| (std::is_unsigned<From>::value
&& std::is_unsigned<To>::value)>::type
* = nullptr)
{
SYMENGINE_ASSERT(f <= std::numeric_limits<To>::max());
SYMENGINE_ASSERT(f >= std::numeric_limits<To>::min());
return static_cast<To>(f);
}
template <typename To, typename From>
inline To numeric_cast(
From f,
typename std::enable_if<(std::is_signed<From>::value
&& std::is_unsigned<To>::value)>::type * = nullptr)
{
#ifdef WITH_SYMENGINE_ASSERT
// Above ifdef is needed to avoid a warning about unused typedefs
typedef typename std::make_unsigned<From>::type unsigned_from_type;
SYMENGINE_ASSERT(f >= 0);
SYMENGINE_ASSERT(static_cast<unsigned_from_type>(f)
<= std::numeric_limits<To>::max());
#endif
return static_cast<To>(f);
}
template <typename To, typename From>
inline To numeric_cast(
From f,
typename std::enable_if<(std::is_unsigned<From>::value
&& std::is_signed<To>::value)>::type * = nullptr)
{
#ifdef WITH_SYMENGINE_ASSERT
typedef typename std::make_unsigned<To>::type unsigned_to_type;
SYMENGINE_ASSERT(
f <= static_cast<unsigned_to_type>(std::numeric_limits<To>::max()));
#endif
return static_cast<To>(f);
}
} // SymEngine
#endif // SYMENGINE_CASTS_H