c++11 学习及测试（shared_ptr, unique_ptr, allocator, function）

智能指针shared_ptr、unique_ptr，构造及使用，make_sheard<typeName>，可以构造sheard_ptr，但是并没有make_unique。。

#include <iostream>
#include <vector>
#include <memory>
using namespace std;

class SharedStrings {
public:
SharedStrings(): _strsPtr(make_shared< vector<string> >()) {
}
void push(const string& s) {
_strsPtr->push_back(s);
}
void show() const {
for_each(_strsPtr->begin(), _strsPtr->end(), [](const string& x){cout << x << endl;});
}
private:
shared_ptr< vector<string> > _strsPtr; //公用元素，省空间
};
int main(int argc, char* argv[]) {

shared_ptr<string> p(new string("wangbing"));
cout << *p << endl;

SharedStrings a;
{
SharedStrings b;
b.push("wangbing");
b.push("WANGBING");
a = b;
}
a.show();

unique_ptr<int> uniq(new int(42));
unique_ptr<int> un2(uniq.release());
//un2.release(); 释放指针所有权，没有被接受，运行期报错
uniq.reset(un2.release());
cout << *uniq << endl;
cout << "Hello world!" << endl;

return 0;
}

内存管理器allocator，四步走：1，分空间（allocate） 2，构造（construct） 3，析构（destroy） 4，释放空间（deallocate）

#include <iostream>
#include <memory>
using namespace std;

int main(int argc, char* argv[]) {
allocator<string> alloc;
int n = 10;
string* p = alloc.allocate(n);
string* q = p;
while(q != p+n) {
alloc.construct(q++, 10, 'w');
cout << *(q-1) << endl;
}
while(q != p) {
alloc.destroy(--q);
}
alloc.deallocate(p, n);
cout << "Hello world!" << endl;

return 0;
}

函数指针的高端写法 function< reType<argType...> >

#include <iostream>
#include <functional>
#include <map>
#include <string>

using namespace std;

class add {
int operator()(int a, int b) const {
return a + b;
}
};

int plu(int a, int b) {
return a + b;
}

class A {
private:
int _a = 0;
public:
A(){}
explicit A(int a): _a(a) {
}
explicit operator bool() const {
return _a != 0;
}
explicit operator int() const {
return _a;
}
};

auto divide = [](int a, int b){return a / b;};
int main(int argc, char* argv[]) {
map<string, function< int(int, int) > > opt{/*{"+", add()},*/
{"+", plu},
{"-", minus<int>()},
{"/", divide},
{"*", [](int a, int b){return a*b;}}};
cout << opt["+"](8, 4) << endl;
cout << opt["-"](8, 4) << endl;
cout << opt["*"](8, 4) << endl;
cout << opt["/"](8, 4) << endl;
A a;
if(a) {
cout << "wangbing" << endl;
} else {
cout << "hehe" << endl;
}
int b = static_cast<int>(a) + 10;

cout << b << endl;
cout << "Hello world!" << endl;

return 0;
}