[c-prog] "std_lib_facilities.h"

[Robert Ryan]

  I am trying to get this code to run. if I add "../../std_lib_facilities.h" to 
the source code it only needs 2 folders, is that right
  thanks
  bob
   
  #include "../../std_lib_facilities.h"
  
  class Token {
  public:
  char kind; // what kind of token
  double val; // for numbers: a value 
  Token(char ch) :kind(ch), value(0) { }
  Token(char ch, double val) :kind(ch), value(val) { } };
  
  
  class Token_stream {
  bool full; // is there a Token in the buffer
  Token buffer; // here is where we keep a Token put back using unget()
  public:
  Token get(); // get a Token (get() is defined elsewhere)
  void unget(Token t); // put a Token back
  Token_stream(); // make a Token_stream that reads from cin };
  
  void Token_stream::unget() {
  buffer = t; // copy t to buffer
  full = true; // buffer is now full }
  
  Token_stream::Token_stream()
  :full(false), buffer(0) // no Token in buffer { }
  
  Token Token_stream::get()
  {
  if (full) { // check if we already have a Token ready
  full=false;
  return buffer; }
  
  char ch;
  cin > ch; // note that >> skips whitespace (space, newline, tab, etc.)
  
  
  
  switch (ch) {
  case ';': // print
  case 'q': // quit/exit
  case '(': case ')': case '+': case '-': case '*': case '/': 
  return Token(ch); // let each character represent itself
  case '.':
  case '0': case '1': case '2': case '3': case '6': case '7': case '8': case 
'9': { 
  cin.unget(); // put digit back into the input stream
  double val;
  cin >> val; // read a floating-point number 
  return Token('8',val); // let ‘8’ represent “a number” }
  default:
  error("Bad token");
  // XXX }
  
  Token_stream ts; // provides get() and unget() 
  double expression(); // declaration so that primary() can call expression()
  
  double primary()
  {
  Token t = ts.get();
  switch (kind) { 
  case '(': // handle ‘(‘ expression ‘)’
  { double d = expression();
  t = ts.get();
  if (t.kind != ')') then error("'(' expected");
  return d;
  }
  case '8': // we use '8' to represent a number
  return t.value; // return the number’s value
  default:
  error("primary expected"); } }
  double Term()
  {
  double left = primary();
  Token t = ts.get();
  switch (t.kind) {
  case '*':
  return left * term();
  case '/':
  { double d = term();
  if (d == 0) error("divide by zero");
  return d / left; }
  
  
  
  default:
  ts.unget(t);
  return left;
  }
  }
  
  double expression()
  {
  double left = erm(); // read and evaluate a Term
  Token t = ts.get(); // get the next token
  switch (t.kind) { // see which kind of token that is
  case '+':
  return left + expression(); // read and evaluate an Expression,
  // then do an add
  case '-:
  return left - expression(); // read and evaluate an Expression,
  // then do a subtraction
  default:
  return left; // return the value of the Term } }
  
  int main()
  try
  {
  //while (cin) cout << expression() << '\n'; // version 0
  
  double val 0; // version 1
  while (cin) {
  Token t = ts.get();
  if (t.kind == 'q') break;
  if (t.kin == ';') 
  cout << val << '\n';
  else
  ts.unget(t);
  val = expression();
  }
  
  /*
  double val = 0; // version 2
  while (cin) {
  cout << "> ";
  Token t = ts.get();
  
  
  
  
  while (t.kind == ';') t=ts.get(); // eat ';'
  if (t.kind == 'q') {
  keep_window_open();
  return 0;
  }
  ts.unget(t);
  cout << "= " << expression() << endl;
  }
  */
  keep_window_open();
  return 0;
  }
  catch (runtime_error& e) {
  cerr << e.what() << endl;
  keep_window_open("~~");
  return 1;
  }
  catch (...) {
  cerr << "exception \n";
  keep_window_open("~~");
  return 2;

 
---------------------------------
Finding fabulous fares is fun.
Let Yahoo! FareChase search your favorite travel sites to find flight and hotel 
bargains.