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@@ -0,0 +1,705 @@
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+#include "stdafx.h"
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+#include <vector>
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+
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+#define WRONG_CODE_ENABLED 0
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+
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+// 0. Basic Form
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+namespace _0
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+{
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+ template <typename T> // Old fasion: template <class T>
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+ class ClassA
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+ {
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+ T a;
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+ T* b;
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+ T foo();
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+ void foo2(T const&);
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+ };
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+
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+ template <int Sz>
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+ class ClassB
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+ {
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+ int arr[Sz];
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+ };
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+
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+ size_t a = sizeof(ClassB<3>);
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+ size_t b = sizeof(ClassB<7>);
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+
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+ template <typename T> void FunctionA(T const& param)
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+ {
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+ }
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+
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+ template <typename T> T FunctionB()
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+ {
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+ return T();
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+ }
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+}
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+
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+// 1.1 Nested in Class
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+namespace _1_1
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+{
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+ template <typename T> // Old fasion: template <class T>
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+ class ClassA
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+ {
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+ T a;
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+ T* b;
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+ T foo();
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+ template <typename U> void foo2(T const&, U const&);
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+ };
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+}
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+
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+// 1.2 Instanciating 1
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+namespace _1_2
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+{
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+ _1_1::ClassA<int> a;
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+
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+ #if WRONG_CODE_ENABLED
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+ _1_1::ClassA<WhatTheFuck> b; // Wrong
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+ _1_1::ClassA c; // Wrong
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+ #endif
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+}
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+
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+// 1.3 Instanciating 2
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+namespace _1_3
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+{
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+ template <typename T>
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+ class ClassB
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+ {
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+ T* a;
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+ };
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+
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+ template <typename T>
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+ class ClassC
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+ {
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+ T a;
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+ };
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+
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+ struct StructA; // Declared but not be defined
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+ ClassB<StructA> d; // Right
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+#if WRONG_CODE_ENABLED
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+ ClassC<StructA> e; // Wrong
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+#endif
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+}
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+
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+// 1.4 Specialization, Partial Specialization, Full Specialization
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+namespace _1_4
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+{
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+ // Prototype of Templates I: Single Parameter
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+ template <typename T> class ClassD
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+ {
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+ int a;
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+ };
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+
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+ // Specialization: Write a pattern for matching
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+ template <> class ClassD<int> // 1. template <> 2. ClassD<int>
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+ {
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+ int b;
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+ };
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+
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+ template <> class ClassD<float>
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+ {
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+ int c;
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+ };
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+
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+ // Partial-Specialization: A partial pattern for matching
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+ template <typename T> class ClassD<T*> // 1. template <typename T> 2. ClassD<T*>
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+ {
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+ int d;
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+ };
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+
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+ template <> class ClassD<int*> // 1. template <> 2. ClassD<T*>
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+ {
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+ int e;
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+ };
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+
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+ // Question:
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+
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+ // ClassD<int>::?
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+ // ClassD<float>::?
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+ // ClassD<double>::?
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+ // ClassD<double*>::?
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+ // ClassD<int*>::?
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+ // ClassD<int const*>::?
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+
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+ // Prototype of Templates II: Multiple Parameter
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+ template <typename T, typename U> class ClassE
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+ {
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+ int a;
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+ };
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+
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+ template <typename T, typename U> class ClassE<T, U*>
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+ {
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+ int b;
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+ };
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+
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+ template <typename T> class ClassE<T, int>
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+ {
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+ int c;
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+ };
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+
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+ template <typename T> class ClassE<T, int*>
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+ {
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+ int d;
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+ };
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+
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+ template <typename U> class ClassE<int, U>
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+ {
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+ int e;
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+ };
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+
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+ template <> class ClassE<int, int>
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+ {
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+ int f;
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+ };
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+
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+ // Question:
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+
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+ // ClassE<float, double>::?
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+ // ClassE<float, int>::?
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+ // ClassE<int, float>::?
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+ // ClassE<int, int*>::?
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+ // ClassE<int, int>::?
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+}
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+
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+// 2.1 Function Specialization
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+namespace _2_1
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+{
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+ // Overload is enabled but no partial-specialization
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+ template <typename T> void foo(T const& x) {}
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+ template <typename T> void foo(T& y) {}
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+ void foo(int&) {}
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+ void foo(int) {}
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+
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+ // Specialization or Overloading
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+ template <> void foo<bool>(bool const& x) {}
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+
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+ // Overloading
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+ template <typename T> void foo(T const*) {}
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+
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+ template <typename T, typename U> void foo2(T const&, U const&);
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+
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+#if WRONG_CODE_ENABLED
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+ template <typename U> void foo2<int, U>(int const&, U const&);
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+ template <typename T, typename U> void foo2<T, U>(int const&, U const&);
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+#endif
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+
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+ // Overloading - Looks like partial specification
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+ template <typename U> void foo2(int const&, U const&);
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+ template <typename T, typename U> void foo2(T const*, U const&);
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+
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+ // Don't forgot
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+ // T foo(...);
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+
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+ // Specialize types which cannot be inferred by parameter
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+ template <typename UninferableT, typename InferableT>
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+ UninferableT foo3(InferableT const&) { return UninferableT(); }
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+
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+ void test()
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+ {
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+
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+ int x = 5;
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+ float y = 10.0f;
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+ foo(y);
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+ int const z = 5;
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+ foo(z);
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+ foo(true);
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+ foo3<int>(0.0f); // Specialize types which is uninferable.
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+
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+#if WRONG_CODE_ENABLED
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+ foo(3); // Ambigous
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+ foo(x); // Ambigous
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+#endif
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+ }
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+}
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+
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+// 2.2 Example: Derived from template.
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+namespace _2_2
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+{
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+ template <typename T>
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+ class ClassA
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+ {
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+ T x;
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+ };
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+
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+ template <typename T>
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+ class ClassB
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+ {
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+ T* x;
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+ };
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+
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+ template <typename T>
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+ class ClassC: public ClassB<T>
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+ {
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+ T* x;
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+ };
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+
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+ ClassC<int> a;
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+
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+#if WRONG_CODE_ENABLED
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+ class ClassC: public ClassA<ClassC>
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+ {
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+ };
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+#endif
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+
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+ class ClassD: public ClassB<ClassD>
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+ {
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+ };
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+
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+ // ClassC =??= ClassD
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+}
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+
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+// 3.1 Meta Switch-Case/If-Then-Else via Specialization
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+namespace _3_1
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+{
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+ bool equal(int a, int b)
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+ {
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+ return a == b;
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+ }
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+
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+ // meta functions:
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+ // bool equal0(TypeA, TypeB)
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+ // {
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+ // return false;
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+ // }
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+ // bool equal1(TypeA, TypeA)
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+ // {
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+ // return true;
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+ // }
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+ // equal(A, A) == equal1(A, A) == true
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+ // euqla(A, B) == equal0(A, B) == false
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+ template <typename T, typename U>
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+ class Equal
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+ {
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+ public:
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+ static bool const value = false;
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+ };
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+
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+ template <typename T>
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+ class Equal<T, T>
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+ {
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+ public:
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+ static bool const value = true;
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+ };
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+
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+ bool x = Equal<int, float>::value;
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+ bool y = Equal<int, int>::value;
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+}
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+
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+// 3.2 SFINAE: Substitution Failure Is Not An Error.
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+namespace _3_2
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+{
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+ class ClassA
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+ {
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+ };
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+
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+ template <int Sz> struct Mark
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+ {
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+ char _[Sz];
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+ };
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+
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+#if WRONG_CODE_ENABLED
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+ template <typename T>
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+ Mark<1> TestIncrementAdd(T const& v)
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+ {
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+ T tmp = v;
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+ ++tmp;
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+ return Mark<1>();
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+ }
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+
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+ template <typename T>
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+ Mark<2> TestIncrementAdd(T const& v)
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+ {
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+ return Mark<2>();
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+ }
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+
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+ bool a = TestIncrementAdd( ClassA() ) ) == sizeof(Mark<1>);
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+#endif
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+
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+ // Right case: From Wiki
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+ class ClassB
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+ {
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+ public:
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+ typedef int Marker;
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+ };
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+
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+ template <typename T> void test(typename T::Marker) { }
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+ template <typename T> void test(T) { }
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+
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+ void DoTest()
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+ {
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+ test<ClassB>(10); // Call #1.
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+ test<int>(10); // Call #2. SFINAE for test(T::Marker).
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+ }
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+}
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+
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+// 3.3 Application: Type Traits
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+namespace _3_3
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+{
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+ template <typename T, typename U> class is_same;
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+
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+
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+ template <typename B, typename D> class is_base_of;
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+ // is_base_of
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+ // 1. B is class, D is also class.
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+ // 2. D* could be convert to B*
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+ // 3. B != D
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+
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+ // Fundamentals
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+ typedef char Accepted;
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+ typedef int Rejected;
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+
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+ class B
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+ {
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+ };
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+
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+ class D: public B
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+ {
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+ };
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+
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+ class D2: public D
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+ {
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+ };
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+
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+ // Type is a class
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+ template <typename T>
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+ class is_class
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+ {
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+ private:
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+ // SFINAE
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+ template <typename U> static Accepted test( int U::* );
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+ template <typename U> static Rejected test(...);
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+
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+ public:
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+ static const bool value = sizeof( test<T>(0) ) == sizeof(Accepted);
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+ };
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+
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+ bool a = is_class<int>::value;
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+ bool b = is_class<B>::value;
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+
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+ // B* could be convert to D*
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+ template <typename Source, typename Dest>
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+ class Convertible
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+ {
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+ private:
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+ // Not SFINAE
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+ static Accepted test(Dest*);
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+ static Rejected test(...);
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+ public:
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+ static const bool value = sizeof( test(static_cast<Source*>(NULL)) ) == sizeof(Accepted);
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+ };
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+
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+ bool c = Convertible<B, D>::value;
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+ bool d = Convertible<D, B>::value;
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+ bool e = Convertible<B, int>::value;
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+
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+ // B != D
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+ using _3_1::Equal;
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+
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+ template <typename Base, typename Derived>
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+ class is_base_of
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+ {
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+ public:
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+ static bool const value =
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+ is_class<Base>::value &&
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+ is_class<Derived>::value &&
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+ Convertible<Base, Derived>::value &&
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+ !Equal<Base, Derived>::value;
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+ };
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+
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+ bool f = is_base_of<B, D2>::value;
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+ bool g = is_base_of<D2, D>::value;
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+ bool h = is_base_of<B, int>::value;
|
|
|
|
+ bool i = is_base_of<float, int>::value;
|
|
|
|
+
|
|
|
|
+ // Questions:
|
|
|
|
+ // remove_reference
|
|
|
|
+ // remove_pointer
|
|
|
|
+ // remove all qualifiers
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+// 3.4 Application: "Recursive" and Meta-Programming
|
|
|
|
+namespace _3_4
|
|
|
|
+{
|
|
|
|
+ // sum a, a+1, ..., b-1, b
|
|
|
|
+ int basic_algo(int a, int b)
|
|
|
|
+ {
|
|
|
|
+ int result = 0;
|
|
|
|
+ for (int i = a; i <= b; ++i)
|
|
|
|
+ {
|
|
|
|
+ result += i;
|
|
|
|
+ }
|
|
|
|
+ return result;
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ // Template could not support variable
|
|
|
|
+
|
|
|
|
+ // sum [a, b] without variable
|
|
|
|
+ int recursive_algo(int a, int b)
|
|
|
|
+ {
|
|
|
|
+ if (a == b)
|
|
|
|
+ {
|
|
|
|
+ return b;
|
|
|
|
+ }
|
|
|
|
+ return a + recursive_algo(a+1, b);
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ // Translate to meta-programming
|
|
|
|
+ template <int a, int b>
|
|
|
|
+ class MetaSum
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ static int const value = MetaSum<a+1, b>::value + a;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ template <int a>
|
|
|
|
+ class MetaSum<a, a>
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ static int const value = a;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ int a = MetaSum<1, 10>::value;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+// 3.5 Application: Meta-Fibonacci
|
|
|
|
+namespace _3_5
|
|
|
|
+{
|
|
|
|
+ template <int Index>
|
|
|
|
+ class Fibonacci
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ static int const value = Fibonacci<Index - 1>::value + Fibonacci<Index - 2>::value;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ template <>
|
|
|
|
+ class Fibonacci<0>
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ static int const value = 0;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ template <>
|
|
|
|
+ class Fibonacci<1>
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ static int const value = 1;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ int a = Fibonacci<8>::value;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+// 4 Directive word: typename and template
|
|
|
|
+namespace _4
|
|
|
|
+{
|
|
|
|
+ // typename T::type x;
|
|
|
|
+ // ??? typename ???
|
|
|
|
+
|
|
|
|
+ // typename T::template U<type> x;
|
|
|
|
+ // ??? template ???
|
|
|
|
+
|
|
|
|
+ class ClassA
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ typedef int NestedType;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ class ClassB
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ typedef ClassA::NestedType NestedType;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ template <typename T>
|
|
|
|
+ class ClassC
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+#if WRONG_CODE_ENABLED
|
|
|
|
+ typedef T::NestedType NestedType;
|
|
|
|
+#endif
|
|
|
|
+ typedef typename T::NestedType NestedType;
|
|
|
|
+ typedef typename std::vector<T>::iterator iterator;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ class ClassD
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ template <typename U, typename V> class NestedType;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ template <typename T>
|
|
|
|
+ class ClassE
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ template <typename U> class NestedType;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ template <typename T, typename U>
|
|
|
|
+ class ClassF
|
|
|
|
+ {
|
|
|
|
+#if WRONG_CODE_ENABLED
|
|
|
|
+ typedef typename T::NestedType<U> NestedType;
|
|
|
|
+#endif
|
|
|
|
+ typedef typename T::template NestedType<U, int> NestedType;
|
|
|
|
+ typedef typename ClassE<T>::template NestedType<U> NestedType2;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ ClassC<ClassB> a;
|
|
|
|
+ ClassF<ClassD, float> b;
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+// 5.1 How to Construct Meta Operators
|
|
|
|
+namespace _5_1
|
|
|
|
+{
|
|
|
|
+ // Expression = Value/Data Structure + Operator/Operations
|
|
|
|
+
|
|
|
|
+ // Value in Templates:
|
|
|
|
+ // Integral Constant (bool, char, unsigned, ...)
|
|
|
|
+ // Type (typename)
|
|
|
|
+
|
|
|
|
+ // 1. Trick: Constant <--> Type
|
|
|
|
+ template <int i>
|
|
|
|
+ class int_
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ static int const value = i;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ int a = int_<5>::value;
|
|
|
|
+
|
|
|
|
+ // This trick could work with overloading
|
|
|
|
+ template <typename T>
|
|
|
|
+ void Do(T* obj, int_<2>)
|
|
|
|
+ {
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ template <typename T>
|
|
|
|
+ void Do(T* obj, int_<1>)
|
|
|
|
+ {
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ void foo()
|
|
|
|
+ {
|
|
|
|
+ Do( static_cast<int*>(nullptr), int_<1>() );
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ template <typename T, int i> void DoAnotherWay(T* obj)
|
|
|
|
+ {
|
|
|
|
+ }
|
|
|
|
+
|
|
|
|
+ // Boolean is more useful than integral in general.
|
|
|
|
+ template <bool v>
|
|
|
|
+ class bool_
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ static bool const value = v;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ typedef bool_<true> true_;
|
|
|
|
+ typedef bool_<false> false_;
|
|
|
|
+
|
|
|
|
+#if WRONG_CODE_ENABLED
|
|
|
|
+ // Aha, function cannot support partial specialization.
|
|
|
|
+ template <typename T> void DoAnotherWay<T, 1>(T* obj) {}
|
|
|
|
+ template <typename T> void DoAnotherWay<T, 2>(T* obj) {}
|
|
|
|
+#endif
|
|
|
|
+
|
|
|
|
+ // 2. Operators:
|
|
|
|
+ // add
|
|
|
|
+
|
|
|
|
+ template <typename T, typename U>
|
|
|
|
+ class add_
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ typedef int_<T::value + U::value> type;
|
|
|
|
+ static int const value = type::value;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+#if WRONG_CODE_ENABLED
|
|
|
|
+ // conflict
|
|
|
|
+ template <int x, int y>
|
|
|
|
+ class add_
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ typedef int_<x+y> type;
|
|
|
|
+ static int const value = type::value;
|
|
|
|
+ };
|
|
|
|
+#endif
|
|
|
|
+ template <int x, int y>
|
|
|
|
+ class add_c
|
|
|
|
+ {
|
|
|
|
+ public:
|
|
|
|
+ typedef int_<x+y> type;
|
|
|
|
+ static int const value = type::value;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ typedef add_< int_<2>, int_<3> >::type sum;
|
|
|
|
+ int b = sum::value;
|
|
|
|
+
|
|
|
|
+ typedef add_< int_<2>, int_<3> >::type sum_c;
|
|
|
|
+ int c = sum_c::value;
|
|
|
|
+
|
|
|
|
+ // another solution
|
|
|
|
+ template <typename T, typename U>
|
|
|
|
+ class add2_: public int_<T::value+U::value>
|
|
|
|
+ {
|
|
|
|
+ };
|
|
|
|
+ int d = add2_< int_<2>, int_<3> >::value;
|
|
|
|
+
|
|
|
|
+ // Other operators: sub, not, or, and ...
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+// 5.2 Example of Meta Programming: Meta-Vector
|
|
|
|
+namespace _5_2
|
|
|
|
+{
|
|
|
|
+ // Array: elem[count]
|
|
|
|
+ // Meta Array ?
|
|
|
|
+
|
|
|
|
+ // Recursively Definition
|
|
|
|
+ // 'Null' terminated
|
|
|
|
+ template <typename HeadT, typename TailT>
|
|
|
|
+ class pair_
|
|
|
|
+ {
|
|
|
|
+ typedef HeadT head;
|
|
|
|
+ typedef TailT tail;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ class Nil;
|
|
|
|
+
|
|
|
|
+ // Try Use It to Definition
|
|
|
|
+ typedef pair_< int, pair_<float, pair_<double, Nil> > > vector_3;
|
|
|
|
+
|
|
|
|
+ template <typename T0, typename T1 = Nil, typename T2 = Nil, typename T3 = Nil>
|
|
|
|
+ class make_vector_
|
|
|
|
+ {
|
|
|
|
+ typedef pair_< T0, make_vector_<T1, T2, T3> > type;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ template <>
|
|
|
|
+ class make_vector_<Nil, Nil, Nil, Nil>
|
|
|
|
+ {
|
|
|
|
+ typedef Nil type;
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ template <typename T0, typename T1 = Nil, typename T2 = Nil, typename T3 = Nil>
|
|
|
|
+ class vector_: public make_vector_<T0, T1, T2, T3>::type
|
|
|
|
+ {
|
|
|
|
+ };
|
|
|
|
+
|
|
|
|
+ typedef vector_<double, float, int> vector3;
|
|
|
|
+
|
|
|
|
+ // Let's meta-program further
|
|
|
|
+ //
|
|
|
|
+ // push_back ? tip: push_back<Vector, Element>::type
|
|
|
|
+ // pop ?
|
|
|
|
+ // find ?
|
|
|
|
+ // size ?
|
|
|
|
+}
|
|
|
|
+
|
|
|
|
+// 6.1 Template-Template Class
|
|
|
|
+
|
|
|
|
+// 6.2 High order function, closure and STL allocator rebind
|
|
|
|
+
|
|
|
|
+int _tmain(int argc, _TCHAR* argv[])
|
|
|
|
+{
|
|
|
|
+ return 0;
|
|
|
|
+}
|
|
|
|
+
|