Monty - Stacks, Queues - LIFO, FIFO

• The objectives of this project are:
• What do LIFO and FIFO mean
• What is a stack, and when to use it
• What is a queue, and when to use it
• What are the common implementations of stacks and queues
• What are the most common use cases of stacks and queues
• What is the proper way to use global variables

Data Structures

The following data structures are used in this project

/**
 * struct stack_s - doubly linked list representation of a stack (or queue)
 * @n: integer
 * @prev: points to the previous element of the stack (or queue)
 * @next: points to the next element of the stack (or queue)
 *
 * Description: doubly linked list node structure
 * for stack, queues, LIFO, FIFO
 */
typedef struct stack_s
{
        int n;
        struct stack_s *prev;
        struct stack_s *next;
} stack_t;

/**
 * struct instruction_s - opcode and its function
 * @opcode: the opcode
 * @f: function to handle the opcode
 *
 * Description: opcode and its function
 * for stack, queues, LIFO, FIFO
 */
typedef struct instruction_s
{
        char *opcode;
        void (*f)(stack_t **stack, unsigned int line_number);
} instruction_t;

Compilation

The code is compiled this way:

gcc -Wall -Werror -Wextra -pedantic -std=c89 *.c -o monty

Opcodes defintion

The following opcodes were implemented:

Name	Description
push	Pushes an element to the stack. Usage: push integer
pall	Prints all the values on the stack, starting from the top of the stack
pint	Prints the value at the top of the stack, followed by a new line
pop	Removes the top element of the stack
swap	Swaps the top two elements of the stack
add	Adds the top two elements of the stack
nop	Does nothing
sub	Subtracts the top element of the stack from the second top element of the stack
div	Divides the second top element of the stack by the top element of the stack
mul	Multiplies the second top element of the stack with the top element of the stack
mod	Computes the rest of the division of the second top element of the stack by the top element of the stack
pchar	Prints the char at the top of the stack, followed by a new line
pstr	Prints the string starting at the top of the stack, followed by a new line
rotl	Rotates the stack to the top
rotr	Rotates the stack to the bottom
stack	Sets the format of the data to a stack (LIFO). This is the default behavior of the program
queue	Sets the format of the data to a queue (FIFO)

Test

Monty 0.98 is a scripting language that is first compiled into Monty byte codes (Just like Python). It relies on a unique stack, with specific instructions to manipulate it. The goal of this project is to create an interpreter for Monty ByteCodes files.

Monty byte code files

Files containing Monty byte codes usually have the .m extension. Most of the industry uses this standard but it is not required by the specification of the language. There is not more than one instruction per line. There can be any number of spaces before or after the opcode and its argument:

julien@ubuntu:~/monty$ cat -e bytecodes/000.m
push 0$
push 1$
push 2$
  push 3$
                   pall    $
push 4$
    push 5    $
      push    6        $
pall$
julien@ubuntu:~/monty$

julien@ubuntu:~/monty$ cat -e bytecodes/001.m
push 0 Push 0 onto the stack$
push 1 Push 1 onto the stack$
$
push 2$
  push 3$
                   pall    $
$
$
                           $
push 4$
$
    push 5    $
      push    6        $
$
pall This is the end of our program. Monty is awesome!$
julien@ubuntu:~/monty$

The monty program

• Usage: monty file
• where file is the path to the file containing Monty byte code
• If the user does not give any file or more than one argument to your program, print the error message USAGE: monty file, followed by a new line, and exit with the status EXIT_FAILURE.
• If, for any reason, it’s not possible to open the file, print the error message Error: Can't open file <file>, followed by a new line, and exit with the status EXIT_FAILURE.
• where <file> is the name of the file.
• If the file contains an invalid instruction, print the error message L<line_number>: unknown instruction <opcode>, followed by a new line, and exit with the status EXIT_FAILURE.
• where is the line number where the instruction appears.
• Line numbers always start at 1.
• The monty program runs the bytecodes line by line and stop if either:
• it executed properly every line of the file.
• it finds an error in the file.
• an error occured.
• If you can’t malloc anymore, print the error message Error: malloc failed, followed by a new line, and exit with status EXIT_FAILURE.
• You have to use malloc and free and are not allowed to use any other function from man malloc (realloc, calloc, …).

Author

• Mendie Uwemedimo.