recycle.cpp

c++编程思想2TICPP-2nd-ed-Vol-two.zip

//: C08:Recycle.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
//{L} Trash
// A Trash Recycler.
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <typeinfo>
#include <vector>
#include "Trash.h"
#include "../purge.h"
using namespace std;

// Sums up the value of the Trash in a bin:
template<class Container>
void sumValue(Container& bin, ostream& os) {
  typename Container::iterator tally = bin.begin();
  float val = 0;
  while(tally != bin.end()) {
    val += (*tally)->weight() * (*tally)->value();
    os << "weight of " << typeid(**tally).name()
       << " = " << (*tally)->weight() << endl;
    ++tally;
  }
  os << "Total value = " << val << endl;
}

int main() {
  srand(time(0)); // Seed the random number generator
  vector<Trash*> bin;
  // Fill up the Trash bin:
  for(int i = 0; i < 30; i++)
    switch(rand() % 3) {
      case 0 :
        bin.push_back(new Aluminum((rand() % 1000)/10.0));
        break;
      case 1 :
        bin.push_back(new Paper((rand() % 1000)/10.0));
        break;
      case 2 :
        bin.push_back(new Glass((rand() % 1000)/10.0));
        break;
    }
  // Note: bins hold exact type of object, not base type:
  vector<Glass*> glassBin;
  vector<Paper*> paperBin;
  vector<Aluminum*> alumBin;
  vector<Trash*>::iterator sorter = bin.begin();
  // Sort the Trash:
  while(sorter != bin.end()) {
    Aluminum* ap = dynamic_cast<Aluminum*>(*sorter);
    Paper* pp = dynamic_cast<Paper*>(*sorter);
    Glass* gp = dynamic_cast<Glass*>(*sorter);
    if(ap) alumBin.push_back(ap);
    else if(pp) paperBin.push_back(pp);
    else if(gp) glassBin.push_back(gp);
    ++sorter;
  }
  sumValue(alumBin, cout);
  sumValue(paperBin, cout);
  sumValue(glassBin, cout);
  sumValue(bin, cout);
  purge(bin);
} ///:~