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refs #628 Add mixins which use the metaclass system instead of the tuple system.

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This commit is contained in:
Mathew Sutcliffe
2016-03-25 19:01:38 +00:00
parent 34bc76e74c
commit 4f3637a046
6 changed files with 273 additions and 0 deletions
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131
src/blackmisc/compare.h
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@@ -13,10 +13,63 @@
#define BLACKMISC_COMPARE_H
#include "blackmisc/tuple.h"
#include "blackmisc/metaclass.h"
#include "blackmisc/inheritancetraits.h"
#include "blackmisc/typetraits.h"
namespace BlackMisc
{
//! \cond PRIVATE
namespace Private
{
template <typename T, typename U>
int compareImpl(const T &a, const U &b, std::true_type)
{
return compare(a, b);
}
template <typename T, typename U>
int compareImpl(const T &a, const U &b, std::false_type)
{
return a < b ? -1 : b < a ? 1 : 0;
}
template <size_t C, size_t I = 0>
struct CompareHelper
{
template <typename T, typename U>
static int compareTuples(const T &a, const U &b)
{
int cmp = compareImpl(std::get<I>(a), std::get<I>(b), HasCompare<std::tuple_element_t<I, T>, std::tuple_element_t<I, U>>());
return cmp ? cmp : CompareHelper<C, I + 1>::compareTuples(a, b);
}
};
template <size_t C>
struct CompareHelper<C, C>
{
template <typename T, typename U>
static int compareTuples(const T &, const U &)
{
return 0;
}
};
}
//! \endcond
/*!
* Lexicographically compare two tuples and return negative, positive, or zero,
* if a is less than, greater than, or equal to b.
* Each element is compared with compare(a', b') if supported by the element type, operator less-than otherwise.
* \todo Rename to compare() after removing tuple.h, which contains a function with the same name and signature.
*/
template <typename... Ts, typename... Us>
int compareTuples(const std::tuple<Ts...> &a, const std::tuple<Us...> &b)
{
static_assert(sizeof...(Ts) == sizeof...(Us), "tuples must be same size");
return Private::CompareHelper<sizeof...(Ts)>::compareTuples(a, b);
}
namespace Mixin
{
@@ -59,6 +112,30 @@ namespace BlackMisc
static bool baseEquals(const CEmpty *, const CEmpty *) { return true; }
};
/*!
* CRTP class template from which a derived class can inherit operator== implemented by metaclass.
*/
template <class Derived>
class EqualsByMetaClass
{
public:
//! Equals
friend bool operator ==(const Derived &a, const Derived &b) { return equals(a, b); }
//! Not equal
friend bool operator !=(const Derived &a, const Derived &b) { return ! equals(a, b); }
private:
static bool equals(const Derived &a, const Derived &b)
{
auto meta = introspect<Derived>().without(MetaFlags<DisabledForComparison>());
return meta.toCaseAwareTuple(a) == meta.toCaseAwareTuple(b) && baseEquals(static_cast<const BaseOfT<Derived> *>(&a), static_cast<const BaseOfT<Derived> *>(&b));
}
template <typename T> static bool baseEquals(const T *a, const T *b) { return *a == *b; }
static bool baseEquals(const void *, const void *) { return true; }
static bool baseEquals(const CEmpty *, const CEmpty *) { return true; }
};
/*!
* CRTP class template from which a derived class can inherit operator< implemented using its compare function.
*
@@ -111,6 +188,37 @@ namespace BlackMisc
static bool baseLess(const CEmpty *, const CEmpty *) { return false; }
};
/*!
* CRTP class template from which a derived class can inherit operator< implemented by metaclass.
*/
template <class Derived>
class LessThanByMetaClass
{
public:
//! Less than
friend bool operator <(const Derived &a, const Derived &b) { return less(a, b); }
//! Greater than
friend bool operator >(const Derived &a, const Derived &b) { return less(b, a); }
//! Less than or equal
friend bool operator <=(const Derived &a, const Derived &b) { return ! less(b, a); }
//! Greater than or equal
friend bool operator >=(const Derived &a, const Derived &b) { return ! less(a, b); }
private:
static bool less(const Derived &a, const Derived &b)
{
if (baseLess(static_cast<const BaseOfT<Derived> *>(&a), static_cast<const BaseOfT<Derived> *>(&b))) { return true; }
auto meta = introspect<Derived>().without(MetaFlags<DisabledForComparison>());
return meta.toCaseAwareTuple(a) < meta.toCaseAwareTuple(b);
}
template <typename T> static bool baseLess(const T *a, const T *b) { return *a < *b; }
static bool baseLess(const void *, const void *) { return false; }
static bool baseLess(const CEmpty *, const CEmpty *) { return false; }
};
/*!
* CRTP class template from which a derived class can inherit non-member compare() implemented by metatuple.
*
@@ -135,6 +243,29 @@ namespace BlackMisc
static int baseCompare(const CEmpty *, const CEmpty *) { return 0; }
};
/*!
* CRTP class template from which a derived class can inherit non-member compare() implemented by metaclass.
*/
template <class Derived>
class CompareByMetaClass
{
public:
//! Return negative, zero, or positive if a is less than, equal to, or greater than b.
friend int compare(const Derived &a, const Derived &b) { return compareImpl(a, b); }
private:
static int compareImpl(const Derived &a, const Derived &b)
{
int baseCmp = baseCompare(static_cast<const BaseOfT<Derived> *>(&a), static_cast<const BaseOfT<Derived> *>(&b));
if (baseCmp) { return baseCmp; }
auto meta = introspect<Derived>().without(MetaFlags<DisabledForComparison>());
return BlackMisc::compareTuples(meta.toCaseAwareTuple(a), meta.toCaseAwareTuple(b));
}
template <typename T> static int baseCompare(const T *a, const T *b) { return compare(*a, *b); }
static int baseCompare(const void *, const void *) { return 0; }
static int baseCompare(const CEmpty *, const CEmpty *) { return 0; }
};
} // Mixin
} // BlackMisc