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Monty

Data structures

/**
 * 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;

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

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:

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$

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:

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 , 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
  • 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, …)

Tasks

  1. push, pall Implement the push and pall opcodes.

The push opcode

The opcode push pushes an element to the stack.

  • Usage: push
    • where is an integer
  • if is not an integer or if there is no argument given to push, print the error message L<line_number>: usage: push integer, followed by a new line, and exit with the status EXIT_FAILURE
    • where is the line number in the file
  • You won’t have to deal with overflows. Use the atoi function

The pall opcode

The opcode pall prints all the values on the stack, starting from the top of the stack.

  • Usage pall
  • Format: see example
  • If the stack is empty, don’t print anything
julien@ubuntu:~/monty$ cat -e bytecodes/00.m
push 1$
push 2$
push 3$
pall$
julien@ubuntu:~/monty$ ./monty bytecodes/00.m
3
2
1
julien@ubuntu:~/monty$

GitHub repository: monty

  1. pint Implement the pint opcode.

The pint opcode

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
julien@ubuntu:~/monty$ cat bytecodes/06.m 
push 1
pint
push 2
pint
push 3
pint
julien@ubuntu:~/monty$ ./monty bytecodes/06.m 
1
2
3
julien@ubuntu:~/monty$
  1. pop Implement the pop opcode.

The pop opcode

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

julien@ubuntu:~/monty$ cat bytecodes/07.m 
push 1
push 2
push 3
pall
pop
pall
pop
pall
pop
pall
julien@ubuntu:~/monty$ ./monty bytecodes/07.m 
3
2
1
2
1
1
julien@ubuntu:~/monty$
  1. swap Implement the swap opcode.

The swap opcode

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

  1. add Implement the add opcode.

The add opcode

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
julien@ubuntu:~/monty$ cat bytecodes/12.m 
push 1
push 2
push 3
pall
add
pall
julien@ubuntu:~/monty$ ./monty bytecodes/12.m 
3
2
1
5
1
julien@ubuntu:~/monty$
  1. nop Implement the nop opcode.

The nop opcode

The opcode nop doesn’t do anything.

Usage: nop

  1. sub Implement the sub opcode.

The sub opcode

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
julien@ubuntu:~/monty$ cat bytecodes/19.m 
push 1
push 2
push 10
push 3
sub
pall
julien@ubuntu:~/monty$ ./monty bytecodes/19.m 
7
2
1
julien@ubuntu:~/monty$
  1. div Implement the div opcode.

The div opcode

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
  • e 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
  1. mul Implement the mul opcode.

The mul opcode

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
  1. mod Implement the mod opcode.

The mod opcode

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

  1. 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).

  2. pchar Implement the pchar opcode.

The pchar opcode

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
julien@ubuntu:~/monty$ cat bytecodes/28.m 
push 72
pchar
julien@ubuntu:~/monty$ ./monty bytecodes/28.m 
H
julien@ubuntu:~/monty$
  1. pstr Implement the pstr opcode.

The pstr opcode

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
julien@ubuntu:~/monty$ cat bytecodes/31.m 
push 1
push 2
push 3
push 4
push 0
push 110
push 0
push 108
push 111
push 111
push 104
push 99
push 83
pstr
julien@ubuntu:~/monty$ ./monty bytecodes/31.m 
School
julien@ubuntu:~/monty$
  1. rotl Implement the rotl opcode.

The rotl opcode

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
julien@ubuntu:~/monty$ 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
julien@ubuntu:~/monty$ ./monty bytecodes/35.m 
0
9
8
7
6
5
4
3
2
1
9
8
7
6
5
4
3
2
1
0
julien@ubuntu:~/monty$
  1. rotr Implement the rotr opcode.

The rotr opcode

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
  1. stack, queue Implement the stack and queue opcodes.

The stack opcode

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

  • Usage: stack

The queue opcode

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
julien@ubuntu:~/monty$ 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
julien@ubuntu:~/monty$ ./monty bytecodes/47.m
1
2
3
6
5
4
1
2
3
11
4
1
2
3
15
1
2
3
11111
julien@ubuntu:~/monty$
  1. Brainfck Write a Brainfck script that prints School, followed by a new line.

You can install the bf interpreter to test your code: sudo apt-get install bf Read: Brainf*ck

julien@ubuntu:~/monty/bf$ bf 1000-school.bf 
School
julien@ubuntu:~/monty/bf$

Directory: bf File: 1000-school.bf

  1. Add two digits Add two digits given by the user.

Read the two digits from stdin, add them, and print the result The total of the two digits with be one digit-long (<10)

julien@ubuntu:~/monty/bf$ bf ./1001-add.bf
81
9julien@ubuntu:~/monty/bf$

Directory: bf File: 1001-add.bf

  1. Multiplication Multiply two digits given by the user.

Read the two digits from stdin, multiply them, and print the result The result of the multiplication will be one digit-long (<10)

julien@ubuntu:~/monty/bf$ bf 1002-mul.bf
24
8julien@ubuntu:~/monty/bf$

Directory: bf File: 1002-mul.bf

  1. Multiplication level up Multiply two digits given by the user.

Read the two digits from stdin, multiply them, and print the result, followed by a new line

julien@ubuntu:~/monty/bf$ bf 1003-mul.bf 
77
49
julien@ubuntu:~/monty/bf$

Directory: bf File: 1003-mul.bf