supervar.cpp

Think in C++ 第二版源码

//: C07:SuperVar.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// A super-variable
#include <iostream>
using namespace std;

class SuperVar {
  enum {
    character,
    integer,
    floating_point
  } vartype;  // Define one
  union {  // Anonymous union
    char c;
    int i;
    float f;
  };
public:
  SuperVar(char ch);
  SuperVar(int ii);
  SuperVar(float ff);
  void print();
};

SuperVar:: SuperVar(char ch) {
  vartype = character;
  c = ch;
}

SuperVar:: SuperVar(int ii) {
  vartype = integer;
  i = ii;
}

SuperVar:: SuperVar(float ff) {
  vartype = floating_point;
  f = ff;
}

void SuperVar::print() {
  switch (vartype) {
    case character:
      cout << "character: " << c << endl;
      break;
    case integer:
      cout << "integer: " << i << endl;
      break;
    case floating_point:
      cout << "float: " << f << endl;
      break;
  }
}

int main() {
  SuperVar A('c'), B(12), C(1.44F);
  A.print();
  B.print();
  C.print();
} ///:~