Monty

This is an interpreter for Monty bytecodes files. Through the esoteric Monty is addressed Linked lists, Stacks, Queues - LIFO, FIFO concepts. Developed on Ubuntu Linux using C language. Bonus track - Brainf*ck

The concepts covered here 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

Requirements

• Linux Ubuntu 14.04 LTS
• gcc (Ubuntu 4.8.4-2ubuntu1~14.04.4) 4.8.4
• C language understanding

Installation

1. Clone the repo in your local machine:
   Example:

vagrant@~$
vagrant@~$ git clone https://github.com/gogomillan/monty.git
vagrant@~$

2. Go to the directory and compile the task you want:
   Example:

vagrant@~$
vagrant@~$ cd monty
vagrant@~$ ls
_add.c  bytecodes        freestack.c  _mod.c   _nop.c    _pint.c  _push.c     README.md  set_number.c  _swap.c
assets  check_command.c  LICENSE      monty.h  _pall.c   _pop.c   _queue.c    _rotl.c    _stack.c
bf      _div.c           main.c       _mul.c   _pchar.c  _pstr.c  readfile.c  _rotr.c    _sub.c
vagrant@~$

3. Complile the project: Example

vagrant@~$
vagrant@~$ gcc -Wall -Werror -Wextra -pedantic \*.c -o monty
vagrant@~$

The Monty language

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. Monty byte code files can contain blank lines (empty or made of spaces only, and any additional text after the opcode or its required argument is not taken into account:

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

Usage

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 , followed by a new line, and exit with the status EXIT_FAILURE

  • where is the name of the file

• If the file contains an invalid instruction, print the error message L<line_number>: unknown instruction , 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

Cases

Case: push, pall

The opcode push pushes an element to the stack.

• Usage: push
  where is an integer
  The opcode pall prints all the values on the stack, starting from the top of the stack.
• Usage pall

vagrant@~$ cat -e bytecodes/00.m
push 1$
push 2$
push 3$
pall$
vagrant@~$ ./monty bytecodes/00.m
3
2
1
vagrant@~$

Case: pint

The opcode pint prints the value at the top of the stack, followed by a new line.

• Usage: pint
  If the stack is empty, print the error message L<line_number>: can't pint, stack empty, followed by a new line, and exit with the status EXIT_FAILURE

vagrant@~$ cat -e bytecodes/00.m
push 1$
push 2$
push 3$
pall$
vagrant@~$ ./monty bytecodes/00.m
3
2
1
vagrant@~$

Case: pop

The opcode pop removes the top element of the stack.

• Usage: pop
  If the stack is empty, print the error message L<line_number>: can't pop an empty stack, followed by a new line, and exit with the status EXIT_FAILURE

vagrant@~$ cat bytecodes/07.m 
push 1
push 2
push 3
pall
pop
pall
pop
pall
pop
pall
vagrant@~$ ./monty bytecodes/07.m 
3
2
1
2
1
1
vagrant@~$ 

Case: swap

The opcode swap swaps the top two elements of the stack.

• Usage: swap
  If the stack contains less than two elements, print the error message L<line_number>: can't swap, stack too short, followed by a new line, and exit with the status EXIT_FAILURE

vagrant@~$ cat bytecodes/09.m 
push 1
push 2
push 3
pall
swap
pall
vagrant@~$ ./monty bytecodes/09.m 
3
2
1
2
3
1
vagrant@~$ 

Case: add

The opcode add adds the top two elements of the stack.

• Usage: add
  • If the stack contains less than two elements, print the error message L<line_number>: can't add, stack too short, followed by a new line, and exit with the status EXIT_FAILURE
  • The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
    • The top element of the stack contains the result
    • The stack is one element shorter

vagrant@~$ cat bytecodes/12.m 
push 1
push 2
push 3
pall
add
pall

vagrant@~$ ./monty bytecodes/12.m 
3
2
1
5
1
vagrant@~$

Case: nop

The opcode nop doesn’t do anything.

• Usage: nop

Case: sub

The opcode sub subtracts the top element of the stack from the second top element of the stack.

• Usage: sub
  If the stack contains less than two elements, print the error message L<line_number>: can't sub, stack too short, followed by a new line, and exit with the status EXIT_FAILURE The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
  • The top element of the stack contains the result
  • The stack is one element shorter

vagrant@~$ cat bytecodes/19.m 
push 1
push 2
push 10
push 3
sub
pall
vagrant@~$ ./monty bytecodes/19.m 
7
2
1
vagrant@~$

Case: div

The opcode div divides the second top element of the stack by the top element of the stack.

• Usage: div
  • If the stack contains less than two elements, print the error message L<line_number>: can't div, stack too short, followed by a new line, and exit with the status EXIT_FAILURE
  • The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
    • The top element of the stack contains the result
    • The stack is one element shorter
  • If the top element of the stack is 0, print the error message L<line_number>: division by zero, followed by a new line, and exit with the status EXIT_FAILURE

vagrant@~$ cat bytecodes/20.m 
push 3
push 10
push 2
pall
div
pall
vagrant@~$ ./monty bytecodes/20.m 
2
10
3
5
3
vagrant@~$

Case: mul

The opcode mul multiplies the second top element of the stack with the top element of the stack.

• Usage: mul
  • If the stack contains less than two elements, print the error message L<line_number>: can't mul, stack too short, followed by a new line, and exit with the status EXIT_FAILURE
  • The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
    • The top element of the stack contains the result
    • The stack is one element shorter
      Try it out ;-)

Case: mod

The opcode mod computes the rest of the division of the second top element of the stack by the top element of the stack.

• Usage: mod
  • If the stack contains less than two elements, print the error message L<line_number>: can't mod, stack too short, followed by a new line, and exit with the status EXIT_FAILURE
  • The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
    • The top element of the stack contains the result
    • The stack is one element shorter
  • If the top element of the stack is 0, print the error message L<line_number>: division by zero, followed by a new line, and exit with the status EXIT_FAILURE

Try it out ;-)

Case: comments

Every good language comes with the capability of commenting. When the first non-space character of a line is #, treat this line as a comment (don’t do anything).
Try it out ;-)

Case: pchar

The opcode pchar prints the char at the top of the stack, followed by a new line.

• Usage: pchar
  • The integer stored at the top of the stack is treated as the ascii value of the character to be printed
  • If the value is not in the ascii table (man ascii) print the error message L<line_number>: can't pchar, value out of range, followed by a new line, and exit with the status EXIT_FAILURE
  • If the stack is empty, print the error message L<line_number>: can't pchar, stack empty, followed by a new line, and exit with the status EXIT_FAILURE

vagrant@~$ cat bytecodes/28.m 
push 72
pchar
vagrant@~$ ./monty bytecodes/28.m 
H
vagrant@~$

Case: pstr

The opcode pstr prints the string starting at the top of the stack, followed by a new line.

• Usage: pstr
  • The integer stored in each element of the stack is treated as the ascii value of the character to be printed
  • The string stops when either:
    • the stack is over
    • the value of the element is 0
    • the value of the element is not in the ascii table
  • If the stack is empty, print only a new line

vagrant@~$ cat bytecodes/31.m 
push 1
push 2
push 3
push 4
push 0
push 110
push 0
push 110
push 111
push 116
push 114
push 101
push 98
push 108
push 111
push 72
pstr
vagrant@~$ ./monty bytecodes/31.m 
Holberton
vagrant@~$ 

Case: rotl

The opcode rotl rotates the stack to the top.

• Usage: rotl
  • The top element of the stack becomes the last one, and the second top element of the stack becomes the first one
  • rotl never fails

vagrant@~$ cat bytecodes/35.m 
push 1
push 2
push 3
push 4
push 5
push 6
push 7
push 8
push 9
push 0
pall
rotl
pall
vagrant@~$ ./monty bytecodes/35.m 
0
9
8
7
6
5
4
3
2
1
9
8
7
6
5
4
3
2
1
0
vagrant@~$ 

Case: rotr

The opcode rotr rotates the stack to the bottom.

• Usage: rotr
  • The last element of the stack becomes the top element of the stack
  • rotr never fails

Try it out ;-)

Case: stack, queue

The opcode stack sets the format of the data to a stack (LIFO). This is the default behavior of the program.

• Usage: stack

The opcode queue sets the format of the data to a queue (FIFO).

• Usage: queue

When switching mode:

• The top of the stack becomes the front of the queue
• The front of the queue becomes the top of the stack

vagrant@~$ cat bytecodes/47.m
queue
push 1
push 2
push 3
pall
stack
push 4
push 5
push 6
pall
add
pall
queue
push 11111
add
pall
vagrant@~$ ./monty bytecodes/47.m
1
2
3
6
5
4
1
2
3
11
4
1
2
3
15
1
2
3
11111
vagrant@~$ 

NOTE: There is bonuses for Brainf**k language that is based un Turin machine find it or contact us ;-)

Authors

• Juan Marcos Cabezas - Initial work - PurpleBoothJMC
• Gonzalo Gomez Millan - Initial work - PurpleBoothGGM

License

This project is licensed under the GNU License - see the LICENSE file for details