# Shell archive made by dwjones on Mon Oct 23 10:00:28 AM CDT 2023

# To install this software on a UNIX system:
#  0) save this text in a file named, for example, shar, on that system
#  1) create a directory (e.g. with the shell command mkdir stack)
#  2) change to that directory (e.g. with the command cd stack),
#  3) direct the remainder of this text to sh (e.g. sh < ../shar).
# This will make sh create files in the new directory; it will do
# nothing else (if you're paranoid, you should scan the following text
# to verify this before you follow these directions).
cat > main.c <<\xxxxxxxxxx
/* main.c -- test my stack of strings */
#include <stdio.h>

#include "stack.h"

unsigned int main() { /* run the test */
    push( " zebra.\n" );
    push( " pet" );
    push( " my" );
    push( " like" );
    push( "I" );
    while( !empty() ) {
	printf( "%s", pop() );
    }
    return 0;
}
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cat > stack.c <<\xxxxxxxxxx
/* stack.c -- implements one instance of a stack class */
#include <stdio.h>
#include <stdlib.h>

#include "stack.h"

struct stack {
    const char * str; /* the string in this stack element */
    struct stack * next; /* link to rest of stack */
};

struct stack * top = NULL;

void push( const char * s ) { /* push s on the stack */
    struct stack * new = malloc( sizeof( struct stack ) );
    new->str = s;
    new->next = top;
    top = new;
}

const char * pop() { /* returns the top of stack and pops */
    const char * ret = top->str;
    struct stack * old = top;
    top = top->next;
    free( old );
    return ret;
}

int empty() { /* reports 1 if stack empty, else 0 */
    return top == NULL;
}
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cat > stack.h <<\xxxxxxxxxx
/* stack.h -- interface to on instance of a stack class */

void push( const char * s ); /* push s on the stack */
const char * pop(); /* returns the top of stack and pops */
int empty(); /* reports 1 if stack empty, else 0 */
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cat > Makefile <<\xxxxxxxxxx
# Makefile for dumb stack demo

demo: main.o stack.o
	cc -o demo main.o stack.o

main.o: main.c stack.h
	cc -c main.c

stack.o: stack.c stack.h
	cc -c stack.c

# make clean -- removes all files created by make
clean:
	rm -f *.o
	rm -f demo
	rm -f shar
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