From 4f8b242a100f3b2cd867cfd8200b20d417dcaaf8 Mon Sep 17 00:00:00 2001 From: Light-City <455954986@qq.com> Date: Tue, 5 Nov 2019 17:27:32 +0800 Subject: [PATCH] update --- README.md | 57 +++++- c++2.0/README.md | 68 +++++++ c++2.0/alias.cpp | 20 +++ c++2.0/auto.cpp | 105 +++++++++++ c++2.0/constexpr.cpp | 36 ++++ c++2.0/decltype.cpp | 52 ++++++ c++2.0/default_delete.cpp | 107 ++++++++++++ c++2.0/explicit.cpp | 83 +++++++++ c++2.0/final.cpp | 33 ++++ c++2.0/hash.cpp | 78 +++++++++ c++2.0/initializer.cpp | 22 +++ c++2.0/lambda.cpp | 224 ++++++++++++++++++++++++ c++2.0/move.cpp | 282 ++++++++++++++++++++++++++++++ c++2.0/noexcept.cpp | 26 +++ c++2.0/nullptr.cpp | 34 ++++ c++2.0/override.cpp | 24 +++ c++2.0/rvalue.cpp | 91 ++++++++++ c++2.0/template_template.cpp | 25 +++ c++2.0/tuple.cpp | 27 +++ c++2.0/type_alias.cpp | 45 +++++ c++2.0/uniform_initialization.cpp | 14 ++ c++2.0/variadic/variadic.cpp | 66 +++++++ c++2.0/variadic/variadic1.cpp | 32 ++++ c++2.0/variadic/variadic2.cpp | 34 ++++ c++2.0/variadic/variadic3_4.cpp | 31 ++++ c++2.0/variadic/variadic5.cpp | 44 +++++ c++2.0/variadic/variadic6.cpp | 52 ++++++ c++2.0/variadic/variadic7.cpp | 57 ++++++ 28 files changed, 1766 insertions(+), 3 deletions(-) create mode 100644 c++2.0/README.md create mode 100644 c++2.0/alias.cpp create mode 100644 c++2.0/auto.cpp create mode 100644 c++2.0/constexpr.cpp create mode 100644 c++2.0/decltype.cpp create mode 100644 c++2.0/default_delete.cpp create mode 100644 c++2.0/explicit.cpp create mode 100644 c++2.0/final.cpp create mode 100644 c++2.0/hash.cpp create mode 100644 c++2.0/initializer.cpp create mode 100644 c++2.0/lambda.cpp create mode 100644 c++2.0/move.cpp create mode 100644 c++2.0/noexcept.cpp create mode 100644 c++2.0/nullptr.cpp create mode 100644 c++2.0/override.cpp create mode 100644 c++2.0/rvalue.cpp create mode 100644 c++2.0/template_template.cpp create mode 100644 c++2.0/tuple.cpp create mode 100644 c++2.0/type_alias.cpp create mode 100644 c++2.0/uniform_initialization.cpp create mode 100644 c++2.0/variadic/variadic.cpp create mode 100644 c++2.0/variadic/variadic1.cpp create mode 100644 c++2.0/variadic/variadic2.cpp create mode 100644 c++2.0/variadic/variadic3_4.cpp create mode 100644 c++2.0/variadic/variadic5.cpp create mode 100644 c++2.0/variadic/variadic6.cpp create mode 100644 c++2.0/variadic/variadic7.cpp diff --git a/README.md b/README.md index 0a6b4a6..d0fe3f0 100644 --- a/README.md +++ b/README.md @@ -40,7 +40,59 @@ #### 2.2 [C++2.0新特性](./c++2.0) -正在更新... +- [Variadic Templates](variadic) +- Spaces in Template Expressions + +```cpp +vector > //ok in each C++ version +vector> // before c++ 11 error error: ‘>>’ should be ‘> >’ within a nested template argument list,c++11后可以正常通过 +``` + +- [nullptr and nullptr_t](nullptr.cpp) +- [Automatic Type Deduction with auto](auto.cpp) +- [Uniform Initialization ](uniform_initialization.cpp) +- [initializer_list](initializer.cpp) +- [explicit for ctors taking more than one argument]( explicit.cpp) +- [range-based for statement](auto.cpp) + +```cpp +for(decl:col) { + statement +} +``` + +- [=default,=delete](default_delete.cpp) + + 如果你自行定义了一个ctor,那么编译器就不会给你一个default ctor + 如果强制加上=default,就可以重新获得并使用default ctor. + +- Alias(化名)Template(template typedef) + +[alias.cpp](alias.cpp) + +[template_template.cpp](template_template.cpp) + +- [template template parameter](template_template.cpp) +- [type alias](type_alias.cpp) +- [noexcept](noexcept.cpp) +- [override](override.cpp) +- [final](final.cpp) +- [decltype](decltype.cpp) +- [lambda](lambda.cpp) +- [Rvalue reference](rvalue.cpp) +- [move aware class](move.cpp) +- 容器-结构与分类 + +(1) 序列式容器包括：array(C++2.0新引入),vector,deque,list,forward_list(C++2.0新引入) + +(2) 关联式容器包括：set/multiset,map/multimap + +(3) 无序容器(C++2.0新引入,更换原先hash_xxx为unordered_xxx)包括：unordered_map/unordered_multimap,unordered_set/unordered_multiset + +- [Hash Function](hash.cpp) +- [tuple](tuple.cpp) + +学习资料：https://www.bilibili.com/video/av51863195?from=search&seid=3610634846288253061 #### 2.3 [C++并发编程v1](./concurrency_v1) @@ -72,8 +124,7 @@ ### 3.代码运行 -代码运行： - 全部在linux下用vim编写，使用gcc/g++调试！全部可正常运行！ +全部在Ubuntu18.04下用vim编写，使用gcc/g++调试！全部可正常运行！ ## 关于作者： diff --git a/c++2.0/README.md b/c++2.0/README.md new file mode 100644 index 0000000..eeee6bc --- /dev/null +++ b/c++2.0/README.md @@ -0,0 +1,68 @@ +## C++ 2.0新特性 + +- [Variadic Templates](variadic) + +- Spaces in Template Expressions + +```cpp +vector > //ok in each C++ version +vector> // before c++ 11 error error: ‘>>’ should be ‘> >’ within a nested template argument list,c++11后可以正常通过 +``` + +- [nullptr and nullptr_t](nullptr.cpp) + +- [Automatic Type Deduction with auto](auto.cpp) + +- [Uniform Initialization ](uniform_initialization.cpp) + +- [initializer_list](initializer.cpp) + +- [explicit for ctors taking more than one argument]( explicit.cpp) + +- [range-based for statement](auto.cpp) + +```cpp +for(decl:col) { + statement +} +``` + +- [=default,=delete](default_delete.cpp) + + 如果你自行定义了一个ctor,那么编译器就不会给你一个default ctor + 如果强制加上=default,就可以重新获得并使用default ctor. + +- Alias(化名)Template(template typedef) + +[alias.cpp](alias.cpp) + +[template_template.cpp](template_template.cpp) + +- [template template parameter](template_template.cpp) + +- [type alias](type_alias.cpp) + +- [noexcept](noexcept.cpp) +- [override](override.cpp) +- [final](final.cpp) +- [decltype](decltype.cpp) + +- [lambda](lambda.cpp) + +- [Rvalue reference](rvalue.cpp) + +- [move aware class](move.cpp) + +- 容器-结构与分类 + +(1) 序列式容器包括：array(C++2.0新引入),vector,deque,list,forward_list(C++2.0新引入) + +(2) 关联式容器包括：set/multiset,map/multimap + +(3) 无序容器(C++2.0新引入,更换原先hash_xxx为unordered_xxx)包括：unordered_map/unordered_multimap,unordered_set/unordered_multiset + +- [Hash Function](hash.cpp) + +- [tuple](tuple.cpp) + +学习自侯捷C++11标准 \ No newline at end of file diff --git a/c++2.0/alias.cpp b/c++2.0/alias.cpp new file mode 100644 index 0000000..9a77183 --- /dev/null +++ b/c++2.0/alias.cpp @@ -0,0 +1,20 @@ +// +// Created by light on 19-11-3. +// + +#include + +using namespace std; + +// 不可以对alias template做偏特化或全特化 +template +using Vec=vector>; // alias template using新用法 +//# define Vec template vector> // 使用宏不行 + +int main() { + Vec col; +// 如果使用宏上述会被替换为template vector> error 不是我们想要的 +// typedef vector> Vec; // typedef也无法做到,没法指定模板参数 + + return 0; +} \ No newline at end of file diff --git a/c++2.0/auto.cpp b/c++2.0/auto.cpp new file mode 100644 index 0000000..bfad975 --- /dev/null +++ b/c++2.0/auto.cpp @@ -0,0 +1,105 @@ +// +// Created by light on 19-11-2. +// + +#include +#include +#include +#include +#include +#include + +using namespace std; + +// iterator stl_iterator.h里面的源码 使用auto +template +#if __cplusplus < 201103L +inline typename reverse_iterator<_Iterator>::difference_type + operator-(const reverse_iterator<_Iterator>& __x, + const reverse_iterator<_Iterator>& __y) +#else +inline auto +operator-(const reverse_iterator<_Iterator> &__x, + const reverse_iterator<_Iterator> &__y) +-> decltype(__x.base() - __y.base()) +#endif +{ return __y.base() - __x.base(); } + + +// auto 关键字(c++11) 语法糖 +// for 循环 ranged-base for + + + +class C { +public: + explicit C(const string &s) : mystr(s) { + + } + + friend ostream &operator<<(ostream out, const C &c) { + out << c.mystr << endl; + } + +private: + string mystr; +}; + +int main() { + + auto i = 42; // 编译器具备实参推导 + + auto ll1 = [](int x) -> int { + return x + 10; + }; + // lambda 匿名函数 + function ll = [](int x) -> int { + return x + 10; + }; + + cout << ll(10) << endl; + list l{1, 2, 3}; + list::iterator iterator; + iterator = find(l.begin(), l.end(), 10); + + auto ite = find(l.begin(), l.end(), 11); // auto 关键字 + + vector vec; + //=====================range-based for statement========================= + // (1) + for (auto elem:vec) // pass by value + cout << elem << endl; + // c++2.0 之前 (2) 编译器会把(1)转换为(2)或(3) + for (auto _pos = l.begin(), _end = l.end(); _pos != _end; ++_pos) + cout << *_pos << " "; + cout << endl; + // (3) + // c++2.0之后 全局函数begin(container)与end(container) 可以接受容器 + for (auto _pos = begin(l), _end = end(l); _pos != _end; ++_pos) + cout << *_pos << " "; + cout << endl; + + // (4) + for (auto &elem:vec) // pass by reference + elem *= 3; + + // (5) 编译器会把(4)转换为(5) + for (auto _pos = l.begin(), _end = l.end(); _pos != _end; ++_pos) { + auto &elem = *_pos; + elem *= 3; + } + cout << endl; + + vector vs = {"hello", "world"}; + // 加了explicit就不能转了 error +// for (const C &elem:vs) { +// } + // auto 不利：降低代码可读性、可能得不到你预想的类型、配合decltype有意想不到的结果 + // auto可能得不到你预想的类型，如vector[]的返回类型。 + vector v(true); + auto var = v.at(0); + cout<< typeid(var).name()< +#include +using namespace std; + +// 对于修饰Object来说: +// const并未区分出编译期常量和运行期常量 +// constexpr限定在了编译期常量 +// constexpr作用：优化!效率! +// constexpr修饰的函数，返回值不一定是编译期常量。It is not a bug, it is a feature. +// const修饰的是类型，constexpr修饰的是用来算出值的那段代码。 +/** + * constexpr修饰的函数，简单的来说，如果其传入的参数可以在编译时期计算出来，那么这个函数就会产生编译时期的值。 + * 但是，传入的参数如果不能在编译时期计算出来，那么constexpr修饰的函数就和普通函数一样了。不 + * @param i + * @return + */ +constexpr int foo(int i) +{ + return i+10; +} + +int main() +{ + int i = 10; + std::array arr; // OK + + foo(i); // Call is Ok + + std::array arr1; // error: the value of ‘i’ is not usable in a constant expression + +} + diff --git a/c++2.0/decltype.cpp b/c++2.0/decltype.cpp new file mode 100644 index 0000000..3aeff91 --- /dev/null +++ b/c++2.0/decltype.cpp @@ -0,0 +1,52 @@ +// +// Created by light on 19-11-3. +// + +#include +#include +#include + +using namespace std; + +// 1.used to declare return tyoes 返回类型 + +// c++2.0之前编译不出来 +//template +//decltype(x + y) add(T1 x, T2 y); + +// 编译器编不出来在2.0之后变成下面这个,先用auto暂定,后面返回类型为decltype(x+y) +template +auto add(T1 x, T2 y) -> decltype(x + y) { // -> 也用在lambda + return x + y; +} + +class Person { +public: + string firstname; + string lastname; +}; +int main() { + + // 1.used to declare return tyoes + cout << add(1, 2) << endl; + + // 2.模板元编程 例如在一个模板函数或类获取容器的value_type,这里就不封装了,直接写在main函数里面 + // 获得表达式的type 有点像typeof()特点 + map coll; + // 获取上述类型 + decltype(coll)::value_type m{"as", 1}; // value_type为pair m + cout << m.first << " " << m.second << endl; + pair p{"a", 2}; + cout << p.first << " " << p.second << endl; + // 3.used to pass the type of a lambda + + // 比大小 + auto cmp = [](const Person &p1, const Person &p2) { + return p1.lastname< p2.lastname; + }; + + // 对于lambda,我们往往只有object,很少有人能够写出它的类型，而有时就需要知道它的类型,要获得其type,就要借助其decltype + set col(cmp); + + return 0; +} \ No newline at end of file diff --git a/c++2.0/default_delete.cpp b/c++2.0/default_delete.cpp new file mode 100644 index 0000000..624b4b6 --- /dev/null +++ b/c++2.0/default_delete.cpp @@ -0,0 +1,107 @@ +// +// Created by light on 19-11-3. +// + +#include +#include + +using namespace std; + +class Zoo { + +public: + Zoo(int a, int b) : a(a), b(b) { + cout << "with param ctor \n"; + } + + Zoo() = default; + + Zoo(const Zoo &) = delete; // copy ctor + + Zoo(Zoo &&) = default; // move ctor + + Zoo &operator=(const Zoo &) = default; // copy assignment + + Zoo &operator=(const Zoo &&) = delete; // move assignment + + // 一般函数可以使用=default或=delete? +// void fun1()= default; // error: ‘void Zoo::fun1()’ cannot be defaulted + void fun1() = delete; // compile ok + // 析构函数可以使用=default或=delete? +// ~Zoo()= delete; // ok,但是造成使用Zoo object出错 + ~Zoo() = default; + + // 上述得出=delete可以使用在任何函数身上,而=default不可以使用在普通函数上 + // 上述会联想到=0,=0只能用在virtual funciton上 + +private: + int a, b; +}; + +class Empty { +}; + +// 等价于 编译器给出的默认版本函数都是public且inline +class Empty1 { +public: + Empty1() {} + + Empty1(const Empty1 &rhs) {} + + ~Empty1() {} +}; + +// no-copy +// copy ctor与copy assignment都delete掉 +struct NoCopy { + NoCopy() = default; + + NoCopy(const NoCopy &) = delete; + + NoCopy &operator=(const NoCopy &) = delete; + + ~NoCopy() = default; +}; + +// no-dtor +struct NoDtor { + NoDtor() = default; + + ~NoDtor() = delete; +}; + +// 对no-copy的改进 将copy ctor与copy assignment 放到private ,但是可以对member与friend调用 +// boost::noncopyable 就用到了PrivateCopy +class PrivateCopy { +private: + PrivateCopy(const PrivateCopy &) {}; + + PrivateCopy &operator=(const PrivateCopy &) {}; + +public: + PrivateCopy() = default; + + ~PrivateCopy() {}; +}; + +// 继承了的都拥有PrivateCopy性质 +class Foo : public PrivateCopy { + +}; + +int main() { + Zoo z; + Zoo z1(1, 2); +// Zoo z2=z; // error copy ctor delete + z = z1; + complex a; // 内部不带指针的可以不用写 big three 没有析构 有copy ctor与copy assignmetn 都是使用=default,没有自己写 + string s; // 内部带指针的有big five + +// NoDtor n; //error no-dtor 不能够自动delete +// NoDtor *p=new NoDtor; // ok +// delete p; // error no-dtor 不能够delete + Foo foo; + Foo foo1; +// foo = foo1; // 继承了的都拥有PrivateCopy性质 + return 0; +} \ No newline at end of file diff --git a/c++2.0/explicit.cpp b/c++2.0/explicit.cpp new file mode 100644 index 0000000..f7f39ba --- /dev/null +++ b/c++2.0/explicit.cpp @@ -0,0 +1,83 @@ +// +// Created by light on 19-11-3. +// + +#include + +using namespace std; + +// non-explicit-one-argument ctor +class Fraction { +public: + // non-explicit-one-argument ctor 可以把别的东西转换为Fraction这种 + Fraction(int num, int den = 1) : m_numerator(num), m_denominator(den) {} + + Fraction operator+(const Fraction &f) { + return Fraction(this->m_numerator + f.m_numerator); + } + + + void getNumAndDen() { + cout << m_numerator << " " << m_denominator << endl; + } + +private: + int m_numerator; // 分子 + int m_denominator; // 分母 +}; + +// explicit-one-argument ctor +class Fraction1 { +public: + // explicit-one-argument ctor 可以把别的东西转换为Fraction这种 + explicit Fraction1(int num, int den = 1) : m_numerator(num), m_denominator(den) {} + + Fraction1 operator+(const Fraction1 &f) { + return Fraction1(this->m_numerator + f.m_numerator); + } + + + void getNumAndDen() { + cout << m_numerator << " " << m_denominator << endl; + } + +private: + int m_numerator; // 分子 + int m_denominator; // 分母 +}; + +class P { +public: + P(int a, int b) { + cout << "P(int a,int b)\n"; + } + + P(int a, int b, int c) { + cout << "non-explicit P(int a,int b,int c)\n"; + } + explicit P(int a, int b, int c,int d) { + cout << "explicit P(int a,int b,int c,int d)\n"; + } +}; + +void fp(const P &) { + +} + +int main() { + Fraction f(3, 5); + Fraction ff = f + 3; // 会将3转换为(3,1) 隐式转换 + ff.getNumAndDen(); + + // 如果不想编译器进行隐式转换,可以在前面添加explicit关键字 + + // c++2.0之前explicit只禁止"存在单一实参"转换 + // c++2.0之后explicit可以进制"多个实参"转换 +// Fraction1 f1(3,5); +// Fraction1 f2 = f1+3; // 会将3转换为(3,1) 不会隐式转换 error: no match for ‘operator+’ (operand types are ‘Fraction1’ and ‘int’) +// f2.getNumAndDen(); + P p1 = {77, 5}; + P p2 = {77, 5, 89}; +// P p3 = {77, 5, 89,99}; //error: converting to ‘P’ from initializer list would use explicit constructor ‘P::P(int, int, int, int)’ + return 0; +} diff --git a/c++2.0/final.cpp b/c++2.0/final.cpp new file mode 100644 index 0000000..843b778 --- /dev/null +++ b/c++2.0/final.cpp @@ -0,0 +1,33 @@ +// +// Created by light on 19-11-3. +// + +#include + +using namespace std; + +// final关键字用于两个地方 +// 第一个用在类，用于说明该类是继承体系下最后的一个类，不要其他类继承我，当继承时就会报错。 +class Base final { +public: + Base() {} + + virtual void func() {} +}; + +class Derivered : public Base { // error: cannot derive from ‘final’ base ‘Base’ in derived type ‘Derivered’ +}; +// 第二个用在虚函数，表示这个虚函数不能再被override了，再override就会报错。 +class Base1 { +public: + Base1() {} + + virtual void func() final {} +}; + +class Derivered1 : public Base1 { + virtual void func() {} // error: overriding final function ‘virtual void Base1::func()’ +}; +int main() { + +} \ No newline at end of file diff --git a/c++2.0/hash.cpp b/c++2.0/hash.cpp new file mode 100644 index 0000000..51355aa --- /dev/null +++ b/c++2.0/hash.cpp @@ -0,0 +1,78 @@ +// +// Created by light on 19-11-4. +// + +#include +#include +#include + + +using namespace std; + +class Customer { + +}; + +// 形式一 通过一个类，重载了操作符()的方式，形成了一个仿函数（函数对象） +class CustomerHash { +public: + size_t operator()(const Customer &c) const { +// return ...; + } +}; + +// 形式二 这个方法实际是通过指定了一个函数指针的方式来通知容器，对于这个自定义类到底应该使用哪个hash function +size_t customer_hash_func(const Customer &t) { +// return ...; +} +// 形式三 以struct hash 偏特化形式实现hash function +namespace std { // 必须放在std里面 + template<> + struct hash : public __hash_base { // 继承不继承都可以! + size_t + operator()(const Customer&s) const noexcept { +// return ...; + } + }; +} + + +// 万能的HashFunction 使用variadic templates + +// (4) +template +inline void hash_combine(size_t& seed, const T& val){ + seed = std::hash()(val) + 0x9e3779b9 + + (seed << 6) + (seed >> 2); +} + +// (3) +template +inline void hash_val(size_t& seed, const T& val){ + hash_combine(seed, val); +} + +// (2) +template +inline void hash_val(size_t& seed, const T& val, const Types&... args){ + hash_combine(seed, val); + hash_val(seed, args...); +} +// (1) +template +inline size_t hash_val(const Types&... args){ + size_t seed = 0; + hash_val(seed, args...); + return seed; +} + + +int main() { + unordered_set unorderedSet; + unordered_setcustset(20,customer_hash_func); + unordered_set unset; + int *p= reinterpret_cast(new Customer()); + cout< +#include +using namespace std; + +int main() { + int i; + int j(); // 0 + int *p; + int *q(); // nullptr + +// int x1{5.0}; // error:narrowing conversion + // 编译器调用initializer_list私有构造之前,编译器准备好array(array头)与len,传递给该构造,并没有内含这个array, + // 指针指向array,copy只是浅copy. + // 如今所有容器都接受任意数量的值 insert()或assign() max() min() + + cout< +#include +#include +#include +#include + +using namespace std; + +// [introducer](optional)mutable throwSpec->retType {} +// mutable决定[]能够被改写 mutable throwSpec retType都是选择的,只要有一个存在就得写() +// retType 返回类型 +// ()放参数 +// []放外面变量 passed by value or reference + + +class UnNamedLocalFunction { +private: + int localVar; +public: + UnNamedLocalFunction(int var) : localVar(var) {} + + bool operator()(int val) { + return val == localVar; + } +}; + +class Person { +public: + string firstname; + string lastname; +}; + +class LambdaFunctor { +public: + LambdaFunctor(int a, int b) : m_a(a), m_b(b) {} + + bool operator()(int n) const { + return m_a < n && n < m_b; + } + +private: + int m_a; + int m_b; +}; + +class X { +private: + int __x, __y; +public: + X(int x, int y) : __x(x), __y(y) {} + + int operator()(int a) { return a; } + + int f() { + // 下列 lambda 的语境是成员函数 X::f + // 对于[=]或[&]的形式，lambda 表达式可以直接使用 this 指针 + return [&]() -> int { + return operator()(this->__x + __y); // X::operator()(this->x + (*this).y) + // 拥有类型 X* + }(); + } + + + int ff() { + return [this]() { + return this->__x; + }(); + } +}; + +int main() { + + [] { + cout << "hello" << endl; + }(); + + auto I = [] { + cout << "hello" << endl; + }; + I(); + int id = 0; + // 先看前面的id 如果没有mutable error: increment of read-only variable ‘id’ + auto f = [id]()mutable { + cout << "id=" << id << endl; + ++id; + }; + id = 42; + f(); // 0 + f(); // 1 + f(); // 2 + cout << id << endl; + + // 上述lambda就相当于 +// class Functor { +// private: +// int id; +// public: +// void operator() { +// cout << "id=" << id << endl; +// ++id; +// } +// }; +// Functor f; + + int id1 = 0; + // 加不加mutable没影响,且传引用只要后面id1被修改了,就会使用修改后的值进行操作 + auto f1 = [&id1]() { + cout << "id1=" << id1 << endl; + ++id1; + }; + id1 = 42; + f1(); // 42 + f1(); // 43 + f1(); // 44 + cout << id1 << endl; + + + // 传参与返回 + int id2 = 0; + auto f2 = [&id2](int ¶m) { + cout << "id2=" << id2 << endl; + ++id2; + ++param; + cout << "param=" << param << endl; + static int x = 5; + return id2; + }; + int param = 1; + f2(param); + cout << "param=" << param << endl; + + // [=] =表示默认以by value传递外部所有变量 + // [&] &表示默认以by reference传递外部所有变量 + auto f3 = [&]() { + cout << "id=" << id << endl; + cout << "id1=" << id1 << endl; + cout << "id2=" << id2 << endl; + cout << "param=" << param << endl; + }; + f3(); + + // 一部分传引用,其余传值 + cout << "id=" << id << endl; + auto f4 = [=, &id]() { // =不可以放在&id后面 + cout << "id=" << id << endl; + id++; + cout << "id1=" << id1 << endl; + cout << "id2=" << id2 << endl; + cout << "param=" << param << endl; + }; + f4(); + + // 一部分传值,其余传引用 + cout << "id=" << id << endl; + auto f5 = [&, id]() { // &不可以放在id后面 + cout << "id=" << id << endl; + cout << "id1=" << id1 << endl; + cout << "id2=" << id2 << endl; + cout << "param=" << param << endl; + }; + f5(); + // this 指针 + X x_(1, 2); + cout << "x_.f()=" << x_.f() << endl; // 1+2=3 + cout << "x_.ff()=" << x_.ff() << endl; // 1 + + + + // 下面lambda函数等价于上述的UnNamedLocalFunction + int tobefound = 5; + auto lambda1 = [tobefound](int val) { + return val == tobefound; + }; + bool b1 = lambda1(5); + UnNamedLocalFunction lambda2(tobefound); + bool b2 = lambda2(5); + cout << b1 << " " << b2 << endl; + + auto ll1 = [](int x) -> int { + return x + 10; + }; + // lambda 匿名函数 + function ll = [](int x) -> float { + return x + 10.0; + }; + cout< cmp = [](const Person &p1, const Person &p2) { + return p1.lastname < p2.lastname; + }; + + + // 对于lambda,我们往往只有object,很少有人能够写出它的类型，而有时就需要知道它的类型,要获得其type,就要借助其decltype + set col(cmp); + + // 要申明lambda对象的类型，可以使用template或者auto进行自动推导。 + // 如果需要知道类型，可以使用decltype，比如，让lambda函数作为关联容器或者无序容器的排序函数或者哈希函数。 + // 上面代码给出了事例（decltype的第三种用法中的事例），定义了一个lambda函数用cmp表示，用来比较Person对象的大小，传入到Set容器中去， + // 但根据右边的set容器的定义，我们传入的不仅是cmp（构造函数），还要传入模板的cmp类型（Set内部需要声明cmp类型）， + // 所以必须使用decltype来推导出类型。 + // （如果没有向构造函数传入cmp，调用的是默认的构造函数，也就是set() : t(Compare()), 这里会报错, 现在不会出问题了! + // 因为Compare()指的是调用默认的lambda构造函数，而lambda函数没有默认构造函数和赋值函数） + + + vector vec{5, 28, 50, 83, 70, 590, 245, 59, 24}; + int x = 30, y = 100; + // 函数对象是很强大的，封装代码和数据来自定义标准库的行为，但需要写出函数对象需要写出整个class，这是不方便的，而且是非本地的， + // 用起来也麻烦，需要去看怎样使用，另外编译出错的信息也不友好，而且它们不是inline的，效率会低一些（算法效率还是最重要的）。 +// vec.erase(remove_if(vec.begin(), vec.end(), LambdaFunctor(x, y)), vec.end()); +// for(auto i:vec) cout< +#include +#include +#include +#include +#include +#include +#include +#include +#include + +using namespace std; + +class MyStringNoMove { +public: + static size_t DCtor; // default-ctor + static size_t Ctor; // ctor + static size_t CCtor; // copy-ctor + static size_t CAsgn; // copy-assignment + static size_t MCtor; // move-ctor + static size_t MAsgn; // move-assignment + static size_t Dtor; // dtor +private: + char *_data; + size_t _len; + + void _init_data(const char *s) { + _data = new char[_len]; + memcpy(_data, s, _len); + _data[_len] = '\0'; + }; +public: + MyStringNoMove() : _data(NULL), _len(0) { ++DCtor; } + + MyStringNoMove(const char *p) : _len(strlen(p)) { + ++Ctor; + _init_data(p); + } + + // copy ctor + MyStringNoMove(const MyStringNoMove &str) { + ++CCtor; + _init_data(str._data); + } + + + // copy assignment + MyStringNoMove &operator=(const MyStringNoMove &str) { + ++CAsgn; + if (this != &str) { + if (_data) delete _data; + _len = str._len; + _init_data(str._data); + } else { + + } + return *this; + } + + ~MyStringNoMove() { // dtor 默认是noexcept + ++Dtor; + if (_data) + delete _data; + } + + bool + operator<(const MyStringNoMove &rhs) const { + return string(this->_data) < string(rhs._data); + } + + bool + operator==(const MyStringNoMove &rhs) const { + return string(this->_data) == string(rhs._data); + } + + char *get() const { + return _data; + } +}; + +size_t MyStringNoMove::DCtor = 0; // default-ctor +size_t MyStringNoMove::Ctor = 0; // ctor +size_t MyStringNoMove::CCtor = 0; // copy-ctor +size_t MyStringNoMove::CAsgn = 0; // copy-assignment +size_t MyStringNoMove::MAsgn = 0; // move-assignment +size_t MyStringNoMove::MCtor = 0; // move-ctor +size_t MyStringNoMove::Dtor = 0; // dtor +// move aware class + +class MyString { +public: + static size_t DCtor; // default-ctor + static size_t Ctor; // ctor + static size_t CCtor; // copy-ctor + static size_t CAsgn; // copy-assignment + static size_t MCtor; // move-ctor + static size_t MAsgn; // move-assignment + static size_t Dtor; // dtor +private: + char *_data; + size_t _len; + + void _init_data(const char *s) { + _data = new char[_len]; + memcpy(_data, s, _len); + _data[_len] = '\0'; + }; +public: + MyString() : _data(NULL), _len(0) { ++DCtor; } + + MyString(const char *p) : _len(strlen(p)) { + ++Ctor; + _init_data(p); + } + + // copy ctor + MyString(const MyString &str) { + ++CCtor; + _init_data(str._data); + } + + // move ctor + MyString(MyString &&str) noexcept: _data(str._data), _len(str._len) { + ++MCtor; + str._len = 0; + str._data = NULL; // 重要 + } + + // copy assignment + MyString &operator=(const MyString &str) { + ++CAsgn; + if (this != &str) { + if (_data) delete _data; + _len = str._len; + _init_data(str._data); + } else { + + } + return *this; + } + + // move assignment + MyString &operator=(MyString &&str) { + ++MAsgn; + if (this != &str) { + if (_data) delete _data; + _data = str._data; + _len = str._len; + str._len = 0; + str._data = NULL; + } else { + + } + return *this; + } + + ~MyString() { // dtor 默认是noexcept + ++Dtor; + if (_data) + delete _data; + } + + bool + operator<(const MyString &rhs) const { + return string(this->_data) < string(rhs._data); + } + + bool + operator==(const MyString &rhs) const { + return string(this->_data) == string(rhs._data); + } + + char *get() const { + return _data; + } +}; + +size_t MyString::DCtor = 0; // default-ctor +size_t MyString::Ctor = 0; // ctor +size_t MyString::CCtor = 0; // copy-ctor +size_t MyString::CAsgn = 0; // copy-assignment +size_t MyString::MAsgn = 0; // move-assignment +size_t MyString::MCtor = 0; // move-ctor +size_t MyString::Dtor = 0; // dtor +namespace std { + template<> + struct hash : public __hash_base { + size_t + operator()(const MyStringNoMove &s) const noexcept { + return hash()(string(s.get())); + } + }; + + template<> + struct hash : public __hash_base { + size_t + operator()(const MyString &s) const noexcept { + return hash()(string(s.get())); + } + }; +} + +template +void output_static_data(const T &myStr) { + cout << typeid(myStr).name() << "==" << endl; + cout << "CCtor=" << T::CCtor + << ",MCtor=" << T::MCtor + << ",CAsgn=" << T::CAsgn + << ",MAsgn=" << T::MAsgn + << ",Dtor=" << T::Dtor + << ",Ctor=" << T::Ctor + << ",DCtor=" << T::DCtor + << endl; +} + + +template +void test_moveable(M c1, NM c2, long &value) { + cout << "\n\ntest, with moveable elements" << endl; + typedef typename iterator_traits::value_type V1type; + clock_t timeStart = clock(); + for (long i = 0; i < value; i++) { + string buf = to_string(i); + auto ite = c1.end(); + c1.insert(ite, V1type(buf.c_str())); + } + cout << "construction,milli-seconds:" << clock() - timeStart << endl; + cout << "size()=" << c1.size() << endl; + output_static_data(*(c1.begin())); + + // 容器本身操作 + timeStart = clock(); + M c11(c1); + cout << "copy, milli-seconds: " << (clock() - timeStart) << endl; + timeStart = clock(); + M c12(move(c1)); + cout << "move copy, milli-seconds: " << (clock() - timeStart) << endl; + timeStart = clock(); + c11.swap(c12); + cout << "swap, milli-seconds: " << (clock() - timeStart) << endl; + + //測試 non-moveable + cout << "\n\ntest, with non-moveable elements" << endl; + typedef typename iterator_traits::value_type V2type; + timeStart = clock(); + for (long i = 0; i < value; ++i) { + string buf = to_string(i); + auto ite = c2.end(); + c2.insert(ite, V2type(buf.c_str())); + } + + cout << "construction, milli-seconds : " << (clock() - timeStart) << endl; + cout << "size()= " << c2.size() << endl; + output_static_data(*(c2.begin())); + + // 容器本身操作 + timeStart = clock(); + NM c21(c2); + cout << "copy, milli-seconds : " << (clock() - timeStart) << endl; + + timeStart = clock(); + NM c22(std::move(c2)); + cout << "move copy, milli-seconds : " << (clock() - timeStart) << endl; + + timeStart = clock(); + c21.swap(c22); + cout << "swap, milli-seconds: " << (clock() - timeStart) << endl; +} + +int main() { + long value = 3000; // vector 测试结果的MCtor与CCtor结果大于3000000,是因为vector的动态扩容,当容量不够的时候,会动态分配并进行拷贝。 +// test_moveable(vector(), vector(), value); +// test_moveable(list(), list(), value); +// test_moveable(deque(), deque(), value); +// test_moveable(multiset(), multiset(), value); +// test_moveable(unordered_multiset(), unordered_multiset(), value); + return 0; +} \ No newline at end of file diff --git a/c++2.0/noexcept.cpp b/c++2.0/noexcept.cpp new file mode 100644 index 0000000..807a6da --- /dev/null +++ b/c++2.0/noexcept.cpp @@ -0,0 +1,26 @@ +// +// Created by light on 19-11-3. +// + +#include +#include + +using namespace std; + +// noexcepte ()中可以加条件 +// 异常可传递 a调用b b抛出异常,a没处理,就会抛出异常 +// 1.异常的回传机制:调用foo如果抛出异常，foo会接着往上层抛出异常， +// 如果最上层没有处理，则会调用terminate函数，terminate函数内部调用abort，使程序退出 + + +// 2.在使用vector deque等容器的移动构造和移动赋值的时候，如果移动构造和移动赋值没有加上noexcept， +// 则容器增长的时候不会调用move constructor，效率就会偏低，所以后面需要加上noexcept，安心使用。 + +void foo() noexcept(true) { +} + +int main() { + foo(); + vector vec; + return 0; +} diff --git a/c++2.0/nullptr.cpp b/c++2.0/nullptr.cpp new file mode 100644 index 0000000..8fa9a7f --- /dev/null +++ b/c++2.0/nullptr.cpp @@ -0,0 +1,34 @@ +// +// Created by light on 19-11-2. +// + +#include +using namespace std; + +void f(int i) { + cout<<"void f(int i)" < + +using namespace std; + +class Base { +public: + Base(){} + virtual void func() {} +}; +class Derivered:public Base{ + virtual void func(int) override {} //error: ‘virtual void Derivered::func(int)’ marked ‘override’, but does not override +}; +// override用于虚函数，上面的virtual void func(int)实际上不是重写父类的虚函数，而是定义一个新的虚函数， +// 我们的本意是重写虚函数，当不加overrride的时候,这样写编译器不会报错， +// 那如果像下面加上override的话，则会报错，表示告诉了编译器，我确实要重写，但写错了，没有重写，于是就报错了, +// 这样就能给我们对虚函数的重写做检查! + +int main() { + +} \ No newline at end of file diff --git a/c++2.0/rvalue.cpp b/c++2.0/rvalue.cpp new file mode 100644 index 0000000..c4cc6cc --- /dev/null +++ b/c++2.0/rvalue.cpp @@ -0,0 +1,91 @@ +// +// Created by light on 19-11-4. +// + +#include +#include +#include + +using namespace std; + +// Rvalue references 解决非必要的拷贝 当赋值右手边是一个"右值",左手边对象可以偷右手边对象,而不需要重新分配内存。 +// 浅copy +int foo() { return 5; } + +class Foo { +public: + Foo() = default; + + Foo(const Foo &foo) = default; + + Foo(Foo &&foo) noexcept {} +}; + + +// 判断调用哪一个函数 +void process(int &i) { + cout << "左值传入" << endl; +} + +void process(int &&i) { + cout << "右值传入" << endl; +} + +void UnPerfectForward(int &&i) { + cout << "forward(int&& i)" << endl; + process(i); +} +// std::forward()实现就是下面这样 +void PerfectForward(int &&i) { + cout << "forward(int&& i)" << endl; + process(static_cast(i)); +} +// Lvalue: 变量 +// Rvalue: 临时对象就是个右值,右值不可以放在左边 +int main() { + int a = 9, b = 4; + + a = b; + b = a; +// a+b=42;// error Rvalue + + string s1("hello"); + string s2("world"); + s1 + s2 = s2; // ok + string() = "ok"; // ok + + cout << "s2:" << s1 + s2 << endl; + cout << "s1:" << s1 << endl; + cout << "s2:" << s2 << endl; + + complex c1(3, 8), c2(1, 0); + c1 + c2 = complex(3, 4); // ok + complex() = complex(1, 2); // ok + + int x = foo(); +// int *p=&foo(); //error! Rvalue不可以取地址 +// foo()=7; // error + // Rvalue references +// vector vec; +// vec.insert(vec.begin(), Foo()); // Rvalue references and Move Semantics + // 原先是下面这个 + // iterator insert(const_iterator __position, const value_type& __x); + // 调用下面这个Move Semantics + // iterator insert(const_iterator __position, value_type&& __x) // 然后转交给Foo(Foo&& foo) + // { return emplace(__position, std::move(__x)); } + // Foo()这个临时对象为右值交给insert的move assignment然后再交给Foo的move ctor。中间有可能会丢失一些信息。 + + int aa = 1; + process(aa); // L + process(1); // R + process(move(aa)); // R + + UnPerfectForward(2); // 希望通过转交调用的是右值传入函数,可是调用的是左值传入 这就是个Unperfect Forwarding + UnPerfectForward(move(aa)); // 同上 + // 那如何设计Perfect Forwarding? + // 为传递加上static_cast强转或者直接使用std::forward() + PerfectForward(2); + PerfectForward(move(aa)); + + return 0; +} \ No newline at end of file diff --git a/c++2.0/template_template.cpp b/c++2.0/template_template.cpp new file mode 100644 index 0000000..5b5f27f --- /dev/null +++ b/c++2.0/template_template.cpp @@ -0,0 +1,25 @@ +// +// Created by light on 19-11-3. +// +#include +#include + +using namespace std; +// template template parameter 模板模板参数 +template class Container> +class XCls { +private: + Container c; +}; + +// alias template +template +using Lst = list; + +int main() { +// XCls mylist1; // error + XCls mylist2; + + return 0; +} diff --git a/c++2.0/tuple.cpp b/c++2.0/tuple.cpp new file mode 100644 index 0000000..aa456bb --- /dev/null +++ b/c++2.0/tuple.cpp @@ -0,0 +1,27 @@ +// +// Created by light on 19-11-4. +// + +#include +#include + +using namespace std; + +// tuple使用 +int main() { + tuple t, t1, t2; + t = make_tuple(1, 2, "qwe"); + t1 = make_tuple(3, 2, "qwe"); + t2 = make_tuple(3, 2, "qwe"); + int a = get<0>(t); + get<0>(t) = get<1>(t); // 可以修改 + cout << a << endl; + cout << (get<0>(t) > get<1>(t) ? "true" : "false") << endl; // 比较大小 + cout << (t1 == t2 ? "true" : "false") << endl; + typedef tuple T; + cout << tuple_size::value << endl; // meta programming 处理类型 + cout << tuple_size::value << endl; + tuple_element<1, T>::type a1 = 10; + cout << a1 << endl; + return 0; +} \ No newline at end of file diff --git a/c++2.0/type_alias.cpp b/c++2.0/type_alias.cpp new file mode 100644 index 0000000..a7aaeb7 --- /dev/null +++ b/c++2.0/type_alias.cpp @@ -0,0 +1,45 @@ +// +// Created by light on 19-11-3. +// + +#include +#include + +using namespace std; + +// 第一种使用 +// type alias +// 等价于typedef void(*func)(int, int); +using fun=void (*)(int, int); + +void example(int, int) {} + +// 第二种使用 +template +struct Container { + using value_type=T; // 等价于typedef T value_type; +}; + +template +void func2(const Cn &cn) { + typename Cn::value_type n; +} + +// 第三种使用 +// alias template +template +using string=basic_string>; +// 等价于 typedef basic_string string; + +// 综上:type alias等价于typedef,没有什么不同 +// using 的所有用法拓展如下: +// 1.using-directives +// using namespace std; or using std::cout; +// 2. using-declaration +// protected: +// using _Base::_M_alloc; +// 3.c++2.0特性 type alias and alias template +int main() { + fun fn = example; // 函数指针 + return 0; +} diff --git a/c++2.0/uniform_initialization.cpp b/c++2.0/uniform_initialization.cpp new file mode 100644 index 0000000..1528078 --- /dev/null +++ b/c++2.0/uniform_initialization.cpp @@ -0,0 +1,14 @@ +// +// Created by light on 19-11-2. +// + +#include +#include + +using namespace std; + +int main() { + int value[]{1, 2, 3}; // initializer_list 会关联一个array 里面元素被编译器逐一分解传给函数 + vector v{2, 3, 5}; + return 0; +} \ No newline at end of file diff --git a/c++2.0/variadic/variadic.cpp b/c++2.0/variadic/variadic.cpp new file mode 100644 index 0000000..3470723 --- /dev/null +++ b/c++2.0/variadic/variadic.cpp @@ -0,0 +1,66 @@ +// +// Created by light on 19-11-2. +// + +// variadic template(c++11) 数量不定的模板参数 +#include +#include +#include + +using namespace std; +// 参数个数 参数个数逐一递减 +// 参数类型 参数类型也逐一递减 + +// (3) +// 需要重载一个终止函数 +template +void _hash(size_t &seed, const T &val) { + cout << "hash over " << val << endl; +} + +// (2) +// 展开函数, 把参数分为一个普通参数和一个参数包，调用一次，参数包大小就减一 +template +void _hash(size_t &seed, const T& val,const Args &... args) { + cout << "parameter " << val<< endl; + // 递归调用自己 + _hash(seed, args...); // 上面如果不给T参数,会自己调用自己成死循环 +} + + +// 泛化版 (1) +template +size_t _hash(const Args &... args) { + cout << "hash start " << endl; + size_t seed = 10; + // 递归调用自己 + _hash(seed, args...); + return seed; +} + + +template +class A { +private: + int size = 0; // c++11 支持类内初始化 +public: + A() { + size = sizeof...(Args); + cout << size << endl; + } +}; + +int main(void) { + size_t f = 10; + _hash("asdas", 2, 3, 4); + A> a; // 类型任意 + + // Tuple就是利用这个特性(变长参数模板) + tuple t = make_tuple(1, "hha"); + int firstArg = get<0>(t); + string secondArg = get<1>(t); + cout << firstArg << " " << secondArg << endl; + return 0; +} + + diff --git a/c++2.0/variadic/variadic1.cpp b/c++2.0/variadic/variadic1.cpp new file mode 100644 index 0000000..4bf9267 --- /dev/null +++ b/c++2.0/variadic/variadic1.cpp @@ -0,0 +1,32 @@ +// +// Created by light on 19-11-4. +// + +#include +#include + +using namespace std; + +// example 1 +void printX() { + +} + +// 特化 +template +void printX(const T &firstArg, const Type &...args) { + cout << firstArg << endl; // 先减少一个做操作 + printX(args...); // 其余的继续分为一个+一包进行递归知道没有了 调用printX() +} + +// 如果写了下面接收任意参数,下面这个跟上面可以共存 泛化版 永远不会被调用,前面特化把它取代了 +template +void printX(const Type &...args) { + printX(args...); +} + + +int main() { + printX(1, "hello", bitset<16>(377), 42); + return 0; +} \ No newline at end of file diff --git a/c++2.0/variadic/variadic2.cpp b/c++2.0/variadic/variadic2.cpp new file mode 100644 index 0000000..c81ebda --- /dev/null +++ b/c++2.0/variadic/variadic2.cpp @@ -0,0 +1,34 @@ +// +// Created by light on 19-11-4. +// + +#include + +using namespace std; + +void print(const char *s) { + while (*s) { + if (*s == '%' && *(++s) != '%') + throw std::runtime_error("invalid format string: missing arguments"); + std::cout << *s++; + } +} + +template +void print(const char *s, T value, Args... args) { + while (*s) { + if (*s == '%' && *(++s) != '%') { + std::cout << value; + print(++s, args...); // 即便当 *s == 0 也会产生调用，以检测更多的类型参数。 + return; + } + std::cout << *s++; + } + throw std::logic_error("extra arguments provided to printf"); +} + +int main() { + int *pi = new int; + print("%d %s %p %f\n", 15, "Acc", pi, 3.14); + return 0; +} \ No newline at end of file diff --git a/c++2.0/variadic/variadic3_4.cpp b/c++2.0/variadic/variadic3_4.cpp new file mode 100644 index 0000000..9771199 --- /dev/null +++ b/c++2.0/variadic/variadic3_4.cpp @@ -0,0 +1,31 @@ +// +// Created by light on 19-11-4. +// + +#include + +using namespace std; + +// 参数type相同的max +int max(initializer_list initializerList) { + int res = *initializerList.begin(); + for (auto elem:initializerList) + res = max(res, elem); + return res; +} + + +// 参数type相同的maximum +int maximum(int n) { + return n; +} + +template +int maximum(int n, Args...args) { + return std::max(n, maximum(args...)); +} + +int main() { + cout << max({10, 8, 100, 1}) << endl; + cout << maximum(57, 48, 60, 100, 20, 18) << endl; +} \ No newline at end of file diff --git a/c++2.0/variadic/variadic5.cpp b/c++2.0/variadic/variadic5.cpp new file mode 100644 index 0000000..3ab70bf --- /dev/null +++ b/c++2.0/variadic/variadic5.cpp @@ -0,0 +1,44 @@ +// +// Created by light on 19-11-4. +// + +#include +#include +#include + +using namespace std; + +// tuple递归调用 + +// 得出这种打印[7,5....,42] +// 需要知道有几个以及现在操作的是第几个 sizeof...() + +// cout<< make_tuple(7.5,string("hello"),bitset<16>(377),47); + + +template +struct print_tuple { + static void print(ostream &os, const tuple &t) { + os << get(t) << (IDX + 1 == MAX ? "" : ","); + print_tuple::print(os, t); + } +}; + +// 偏特化 +template +struct print_tuple { + static void print(ostream &os, const tuple &t) { + } +}; + +template +ostream &operator<<(ostream &os, const tuple &t) { + os << "["; + print_tuple<0, sizeof...(Args), Args...>::print(os, t); + return os << "]"; +} + + +int main() { + cout << make_tuple(7.5, string("hello"), bitset<16>(377), 47) << endl; +} \ No newline at end of file diff --git a/c++2.0/variadic/variadic6.cpp b/c++2.0/variadic/variadic6.cpp new file mode 100644 index 0000000..8a3fe2e --- /dev/null +++ b/c++2.0/variadic/variadic6.cpp @@ -0,0 +1,52 @@ +// +// Created by light on 19-11-4. +// + +#include + + +using namespace std; +// 上一个例子:variadic5.cpp为递归调用 +// 当前这个例子为递归继承 +namespace light { + template + class tuple; + + template<> + class tuple<> { + }; + + template + class tuple : private tuple { + typedef tuple inherited; + protected: + Head m_head; + public: + tuple() {} + + tuple(Head h, Tail...tail) : m_head(h), inherited(tail...) {} + + // decltype()中的m_head必须放到前面,否则编译器找不到 + auto head() -> decltype(m_head) { return m_head; } + // 或者 Head head() { return m_head; } + + inherited &tail() { return *this; } + }; +} +/** + * string 32 8字节对齐 + * float 4 + * int 4 + * 4+4+32=40 自底向上 + */ + +int main() { + using light::tuple; + tuple t(41, 6.3, "nico"); + cout << sizeof(t) << endl; + cout << t.head() << endl; + cout << t.tail().head() << endl; + cout << t.tail().tail().head() << endl; + + return 0; +} diff --git a/c++2.0/variadic/variadic7.cpp b/c++2.0/variadic/variadic7.cpp new file mode 100644 index 0000000..6743455 --- /dev/null +++ b/c++2.0/variadic/variadic7.cpp @@ -0,0 +1,57 @@ +// +// Created by light on 19-11-4. +// + +#include + +using namespace std; + +namespace light { + template + class tuple; + + template<> + class tuple<> { + }; + + template + class tuple { + typedef tuple composited; + protected: + Head m_head; + composited m_tai; + public: + tuple() {} + int get() { return sizeof(composited);} + tuple(Head h, Tail...tail) : m_head(h), m_tai(tail...) {} + + // decltype()中的m_head必须放到前面,否则编译器找不到 + auto head() -> decltype(m_head) { return m_head; } + // 或者 Head head() { return m_head; } + + composited &tail() { return m_tai; } + }; +} + +// 根据string为8字节对齐,我们得出8字节对齐 +// 第一次 int 4字节Head调整到边界8 那composite呢?继续往下分析 +// 第二次 把第一次的composited拆分为float与一包, float也占4字节,调整到8边界为8字节,那这一步的composited呢?继续往下分析 +// 第三次 把第二次的compoisted拆分成sting与一包, string占32字节,已经为8倍数,无需调整,而这一步的composited呢?由于到这里一包已经没了,就会调用它的全特化版本,全特环版本为空,sizeof为1, +// 调整到8的倍数为8. +// 因此最后的内存结构(自底向上)为：8 + 8 + 32 + 8 = 56 64位机器结果 + +struct A { + string a; + float b; +}; +int main() { + using light::tuple; + tuple t(41, 6.3, "nico"); + cout<