#include <iostream>
using namespace std;
class SmallInt
{
public:
SmallInt(int i=0):val(i)
{ if(i<0 || i>255) throw std::out_of_range("Bad SmallInt initializer");}
~SmallInt(void){};
operator int()const
{std::cout<<"Translate SmallInt to Int"<<endl;return val;}
private:
size_t val;
};SmallInt sm; double dv; sm >= dv //sm convet to int and then convert to double if(sm) //sm convet to int and then convert to bool int x = static_cast<int>(si) + 2; // instruct compiler SmallInt to int<3>禁止转换
int cal(int); Integral intVal; cal(intVal); //error,no convertion to int from Integral
SmallInt ->standard type ->standard type //ok standard type ->standard type->SmallInt //ok Integral->SmallInt->Int //error在转换中只能用到一个类类型转换（类类型<->标准类型，类类型<->类类型
class SmallInt
{
public:
SmallInt(int i=0):val(i){ if(i<0 || i>255) throw std::out_of_range("Bad SmallInt
initializer");}
SmallInt(double db):val(db){}
~SmallInt(void){};
operator int()const{std::cout<<"Translate SmallInt to Int"<<endl;return val;}
operator double()const{std::cout<<"Translate SmallInt to double"<<endl;return val;}
private:
size_t val;
};
void fpComputer(float)
{}
SmallInt sm(100);
fpComputer(sm) //error void manip(const SmallInt&); double d; int i; float f; mamip(d); //ok,use SmallInt(double) to convert manip(i); //ok,use SmallInt(int) to convert manip(f); //error,ambiguous
class Integral;
class SmallInt
{
public:
SmallInt(Integral);
//...
};
class Intergal
{
public:
operator SmallInt()const;
//...
}
void compute(SmallInt);
Integral intVal;
compute(intVal); //error:ambiguous这里的Integral类型的变量intVal可以通过构造函数以及类类型转换两种方式转换成SmallInt，所以具有二义性compute(intVal.operator SmallInt()); compute(SmallInt(intVal));
C++primer读书笔记9转换与类类型,布布扣,bubuko.com
原文地址：http://blog.csdn.net/ddupd/article/details/38001773
