generators.h

Think in C++ 第二版源码

//: C21:Generators.h
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// Different ways to fill sequences
#ifndef GENERATORS_H
#define GENERATORS_H
#include <set>
#include <cstdlib>
#include <cstring>
#include <ctime>

// A generator that can skip over numbers:
class SkipGen {
  int i;
  int skp;
public:
  SkipGen(int start = 0, int skip = 1)
    : i(start), skp(skip) {}
  int operator()() {
    int r = i;
    i += skp;
    return r;
  }
};

// Generate unique random numbers from 0 to mod:
class URandGen {
  std::set<int> used;
  int modulus;
public:
  URandGen(int mod) : modulus(mod) { 
    std::srand(std::time(0)); 
  }
  int operator()() {
    while(true) {
      int i = (int)std::rand() % modulus;
      if(used.find(i) == used.end()) {
        used.insert(i);
        return i;
      }
    }
  }
};

// Produces random characters:
class CharGen {
  static const char* source;
  static const int len;
public:
  CharGen() { std::srand(std::time(0)); }
  char operator()() { 
    return source[std::rand() % len];
  }
};

// Statics created here for convenience, but
// will cause problems if multiply included:
const char* CharGen::source = "ABCDEFGHIJK"
  "LMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
const int CharGen::len = std::strlen(source);
#endif // GENERATORS_H ///:~