轉(zhuǎn)換函數(shù)

class A {
public:
   operator double() {
        // return a double value
    }
};

explicit關(guān)鍵字

class A {
public:
    explicit A(int a) {}
};

指定構(gòu)造函數(shù)需要顯式調(diào)用，這樣編譯器就不會(huì)做隱式轉(zhuǎn)換，避免因one-argument構(gòu)造函數(shù)而導(dǎo)致意料之外的類型轉(zhuǎn)換。

pointer-like class

class A {
public:
    T& operator*() {
        return *data;
    }
    T* operator->() {
        return data;
    }
private:
    T* data;
};

function-like class

class A {
public:
    operator() {}
};