effector.txt

Think in C++ 第二版源码

//: C18:Effector.txt
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// (Should be "cpp" but I can't get it to compile with
// My windows compilers, so making it a txt file will
// keep it out of the makefile for the time being)
// Jerry Schwarz's "effectors"
#include<iostream>
#include <cstdlib>
#include <string>
#include <climits> // ULONG_MAX
using namespace std;

// Put out a portion of a string:
class Fixw {
  string str;
public:
  Fixw(const string& s, int width)
    : str(s, 0, width) {}
  friend ostream& 
  operator<<(ostream& os, Fixw& fw) {
    return os << fw.str;
  }
};

typedef unsigned long ulong;

// Print a number in binary:
class Bin {
  ulong n;
public:
  Bin(ulong nn) { n = nn; }
  friend ostream& operator<<(ostream&, Bin&);
};

ostream& operator<<(ostream& os, Bin& b) {
  ulong bit = ~(ULONG_MAX >> 1); // Top bit set
  while(bit) {
    os << (b.n & bit ? '1' : '0');
    bit >>= 1;
  }
  return os;
}

int main() {
  char* string =
    "Things that make us happy, make us wise";
  for(int i = 1; i <= strlen(string); i++)
    cout << Fixw(string, i) << endl;
  ulong x = 0xCAFEBABEUL;
  ulong y = 0x76543210UL;
  cout << "x in binary: " << Bin(x) << endl;
  cout << "y in binary: " << Bin(y) << endl;
} ///:~