Question about stack - push - pop

Hi,

I'm sorry to bother you guys with this but I already used the search button and looked at a lot of threads but I just can't figure it out :(
I'm kind'of a newbie:D

I need to make a program that reads a text file and displays it backwards, this shouldn't be to difficult but I don't have any info on stacks.
I have to make it for my evening class, the teacher told us to use stack but we didn't see this in class and have no idea how this works.

I was hoping someone could help me with this one,...
The part that opens the textfile and displays it on the screen is ready, now I only have to figure out the stack part.


Thanks in advance,

Wietse.

A stack is really very simple, you can implement one quite quickly using an array:

Code:

---

#include <iostream>
#include <string>

const int stack_size = 100;

int main()
{
  // Stack stuff
  int stack_loc = 0;
  std::string stack[stack_size];

  std::string line;

  while ( std::getline ( std::cin, line ) )
    stack[stack_loc++] = line; // Push onto the stack

  while ( stack_loc != 0 )
    std::cout<< stack[--stack_loc] <<std::endl; // Pop off the stack
}

---

The basic idea is to only add and remove at the top of the stack (or end of the array in this case), so when you push (add) a series of items onto the stack, you can then pop them all off and they'll be in reverse order.

-Prelude

thanks for the quick reply.
now it shows I'm new :) there are some things I don't get
what is the std:: for?
And do I need to set a stack length because I don't know how many characters the textfile will have.

For the reading of the file I used this code

Code:

---

# include <iostream.h>
# include <fstream.h>
# include <stdlib.h>

void main()


{
        fstream bestand;
        char letter;
        bestand.open ("c:\\autoexec.bat",ios::in);
        while(!bestand.eof())
        {
                bestand.get(letter);
                cout<<letter;
        }
        bestand.close();
}

---

so instead of getline I could use the char letter.

>what is the std:: for?
It's a scope resolution for names declared in the std namespace. It's a better (if less concise) way of saying

using namespace std;

However, from the code I've seen from you so far it appears you aren't using the current C++ headers, so namespace resolution shouldn't be a worry, just remove every occurance of std::. ;)

>And do I need to set a stack length because I don't know how many characters the textfile will have.
If your stack is implemented as a static array as I used then yes, I imagine you haven't worked with linked data structures yet, so a dynamicly sized stack probably isn't available. Since this is a class project you can just assume a large enough size and leave it at that.

>For the reading of the file I used this code
See my reply to your post here.

-Prelude

I looked at the post and wow :)
that's something else, our teacher told us that that that was the best way to read a file (it's his code).

Yours is smaller and I kinda understand it.

But I can't find how I can connect the 2 codes (reading and stack)
if I remove the std:: before std::string stack[stack_size] as you said I get an error "undeclared identifier".

I feel like I'm waisting your time here, sorry that I bother pro's with newbie questions but I'm trying to learn it :)
The help is really appreciated.

>if I remove the std:: before std::string stack[stack_size] as you said I get an error "undeclared identifier".
This may work better for your purposes (ie. be easier to integrate):

Code:

---

#include <iostream.h>

#define stack_size 100

int main()
{
  // Stack stuff
  int stack_loc = 0;
  char stack[stack_size];

  char c;

  while ( cin.get ( c ) )
    stack[stack_loc++] = c; // Push onto the stack

  while ( stack_loc != 0 )
    cout<< stack[--stack_loc] <<endl; // Pop off the stack
}

---

-Prelude

Thanks a heap,

I managed to put them together.
I learned alot in this half hour.

Untill the next time (possibly tomorrow :) )