support bazel complie this project and format code.

cpp2.0/cpp11/explicit.cpp

@@ -0,0 +1,92 @@
+//
+// Created by light on 19-11-3.
+//
+
+#include <iostream>
+
+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;
+}