{

// 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;

}

int m_numerator; // 分子

int m_denominator; // 分母

{

// 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;

}

int m_numerator; // 分子

int m_denominator; // 分母

{

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";

}

{

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;