simplegenerators.h

C++编程思想第二版第一册答案

//: C20:SimpleGenerators.h
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// Generic generators, including
// one that creates pairs
#include <iostream>
#include <utility>

// A generator that increments its value:
template<typename T>
class IncrGen {
  T i;
public:
  IncrGen(T ii) : i (ii) {}
  T operator()() { return i++; }
};

// A generator that produces an STL pair<>:
template<typename T1, typename T2>
class PairGen {
  T1 i;
  T2 j;
public:
  PairGen(T1 ii, T2 jj) : i(ii), j(jj) {}
  std::pair<T1,T2> operator()() { 
    return std::pair<T1,T2>(i++, j++); 
  }
};

// A generic global operator<< 
// for printing any STL pair<>:
template<typename Pair> std::ostream&
operator<<(std::ostream& os, const Pair& p) {
  return os << p.first << "\t" 
    << p.second << std::endl;
} ///:~