Lab 14: Experiment 1

Working with a stack

The Problem

What happens if we input a bunch of words, push them all onto a stack, and then, as we pop them off, display them?

The Prediction

So what will happen to the words when they're output? Try this on your own first:

Question #14.1.1: The words "Madam I'm Adam" were pushed one after the other onto a stack and then they were printed as they were popped from the stack. What would be printed?

Question #14.1.2: Now predict what will happen in general to any sequence of words.

Design

The behavior of the program you are to write is as follows:

The program will create a new empty stack. It will prompt for and read in a file name from the keyboard and then will open that file for input. Words are read from the file and each is pushed onto the stack .When the end-of-file is reached, the file is closed. Words are then popped from the stack and displayed on the screen (or if you prefer, written to an output file) until the stack is empty.

The objects for this program are quite straightforward:

Description	Type	Kind	Name
the stack of words	stack<string>	varying	theStack
the file name	string	varying	inFileName
the keyboard	istream	varying	cin
the input stream	ifstream	varying	inStream
a word	string	varying	word
the screen	ostream	varying	cout

The operations are fairly straightforward as well. The following list omits the file operations, but you can look them up from previous labs.

Description	Predefined?	Name	Library
create a new stack	yes	stack() constructor	stack
push a word onto the stack	yes	push()	stack
test if stack is empty	yes	empty()	stack
get top value from stack	yes	top()	stack
pop top value from stack	yes	pop()	stack

Declaring a stack is like declaring a vector or list. Use the same syntax, but use "stack" for the container. The other operations will be methods invoked on theStack.

So we end up with this algorithm:

1. Create a new, empty stack theStack.
2. Display a prompt for the input file name.
3. Read inFileName.
4. Open inStream (using inFileName) and test that it opened properly.
5. Loop:
   1. Read word from inStream.
   2. If inStream is at the end-of-file, terminate the loop.
   3. Push word onto theStack.
6. Close inStream.
7. While theStack is not empty:
   1. Display the top of theStack on the screen (followed by some whitespace).
   2. Pop the top value from theStack.

Write the program, compile it, and execute it.

The Analysis

Compare your prediction with the actual outcome.

Question #14.1.3: How closely did your prediction match the actual outcome?

Question #14.1.4: How does LIFO explain the behavior you see from your program?