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14
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ISTACK.CPP
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1995-02-23
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// File from page 574 in "Thinking in C++" by Bruce Eckel
//////////////////////////////////////////////////
// From the compressed package ECKELT01.ZIP 2/21/95
// Copyright (c) Bruce Eckel, 1995
// Source code file from the book "Thinking in C++",
// Prentice Hall, 1995, ISBN: 0-13-917709-4
// All rights reserved EXCEPT as allowed by the following
// statements: You may freely use this file for your own
// work, including modifications and distribution in
// executable form only. You may copy and distribute this
// file, as long as it is only distributed in the complete
// (compressed) package with the other files from this
// book and you do not remove this copyright and notice.
// You may not distribute modified versions of the source
// code in this package. This package may be freely placed
// on bulletin boards, internet nodes, shareware disks and
// product vendor disks. You may not use this file in
// printed media without the express permission of the
// author. Bruce Eckel makes no
// representation about the suitability of this software
// for any purpose. It is provided "as is" without express
// or implied warranty of any kind. The entire risk as to
// the quality and performance of the software is with
// you. Should the software prove defective, you assume
// the cost of all necessary servicing, repair, or
// correction.
// If you think you've found an error, please
// email all modified files with loudly commented changes
// to: eckel@aol.com (please use the same
// address for non-code errors found in the book).
//////////////////////////////////////////////////
//: ISTACK.CPP -- Simple integer stack
#include <assert.h>
#include <iostream.h>
class istack {
enum { ssize = 100 };
int stack[ssize];
int top;
public:
istack() : top(0) { stack[top] = 0; }
void push(int i) {
if(top < ssize) stack[top++] = i;
}
int pop() {
return stack[top > 0 ? --top : top];
}
friend class istackIter;
};
// An iterator is a "super-pointer":
class istackIter {
istack& S;
int index;
public:
istackIter(istack& is)
: S(is), index(0) {}
int operator++() { // Prefix form
if (index < S.top - 1) index++;
return S.stack[index];
}
int operator++(int) { // Postfix form
int returnval = S.stack[index];
if (index < S.top - 1) index++;
return returnval;
}
};
// For interest, generate Fibonacci numbers:
int fibonacci(int N) {
const sz = 100;
assert(N < sz);
static F[sz]; // Initialized to zero
F[0] = F[1] = 1;
// Scan for unfilled array elements:
for(int i = 0; i < sz; i++)
if(F[i] == 0) break;
while(i <= N) {
F[i] = F[i-1] + F[i-2];
i++;
}
return F[N];
}
main() {
istack is;
for(int i=0; i < 20; i++)
is.push(fibonacci(i));
// Traverse with an iterator:
istackIter it(is);
for(i = 0; i < 20; i++)
cout << it++ << endl;
for(i = 0; i < 20; i++)
cout << is.pop() << endl;
}