stack2.cpp

Think in C++ 第二版源码

//: C20:Stack2.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// Converting a list to a stack
#include "../require.h"
#include <iostream>
#include <fstream>
#include <stack>
#include <list>
#include <string>
using namespace std;

// Expects a stack:
template<class Stk>
void stackOut(Stk& s, ostream& os = cout) {
  while(!s.empty()) {
    os << s.top() << "\n";
    s.pop();
  }
}

class Line {
  string line; // Without leading spaces
  int lspaces; // Number of leading spaces
public:
  Line(string s) : line(s) {
    lspaces = line.find_first_not_of(' ');
    if(lspaces == string::npos)
      lspaces = 0;
    line = line.substr(lspaces);
  }
  friend ostream& 
  operator<<(ostream& os, const Line& l) {
    for(int i = 0; i < l.lspaces; i++)
      os << ' ';
    return os << l.line;
  }
  // Other functions here...
};

int main(int argc, char* argv[]) {
  requireArgs(argc, 1); // File name is argument
  ifstream in(argv[1]);
  assure(in, argv[1]);
  list<Line> lines;
  // Read file and store lines in the list:
  string s;
  while(getline(in, s)) 
    lines.push_front(s);
  // Turn the list into a stack for printing:
  stack<Line, list<Line> > stk(lines);
  stackOut(stk);
} ///:~