DMS

Esoteric programming language built for Advent of Code 2023

You can try it in your browser here

Summary

Note

For full details you should read the full specification, this is a simplified cheat sheet

DMS code is broken up into commands, each command evaluates to an integer result, and can change the state of the machine. The resulting integer is added to the current cell.

A command is either an expression, or a unary operator applied to another command. See below for details.

Expressions

Are the simplest building block of commands, representing a single value

Symbol	Name	Returns	Notes
Any sequence of digits 0-9	NUMBER	The base-10 interpretation of those digits as an integer i.e. 123 returns 123	Up to implementation what to do if the number is too large for a 32-bit signed int
' followed by any character C	CHAR	The UTF-16 code point of the character C, i.e 'a returns 97
.	CELL	Value stored in the current cell
%	COMMAND_POINTER	The command pointer
[	CELL_POSITION_X	The X coordinate of the cell pointer
]	CELL_POSITION_Y	The Y coordinate of the cell pointer

Operators

Let I denote the input to each operator for the descriptions of effects and return values.

Symbol	Name	Effect	Returns	Notes
-	NEGATE	No effect on state	-I	-123 is - applied to 123, returning -123
+	SIGN	No effect on state	The sign of I -- 1 if I is positive, -1 if I is negative, 0 otherwise
!	COMPLEMENT	No effect on state	1 - I	!1 returns 0, !0 returns 1, !6 returns -5
?	CONDITION	No effect on state	I if the current cell value is positive. 0 otherwise
_	DISCARD	No effect on state	Always returns 0, ignoring its input	Useful for creating a command that updates the state of the machine but doesn't write anything to the current cell.
@	CHAR_OUTPUT	Writes I, interpreted as a UTF-16 character, to standard output. If I is 0, terminates the program instead	I (unchanged)	Outputting the NUL char (0) is the only way to terminate a DMS program
*	INT_OUTPUT	Writes I, formatted as a base-10 integer, to standard output.	I (unchanged)
:	JUMP	Increases the command pointer by I	I (unchanged)	Jumping past the last command or before the first causes the command pointer to wrap around. Jumping by -1 (:-1) will result in the same command being executed in a loop.
<	LEFT	Decreases cell pointer's X value by I	I (unchanged)	This moves the current cell left by I. Cell positions wrap at the edges of the tape
>	RIGHT	Increases cell pointer's X value by I	I (unchanged)	This moves the current cell right by I. Cell positions wrap at the edges of the tape
^	UP	Decreases cell pointer's Y value by I	I (unchanged)	This moves the current cell up by I. Cell positions wrap at the edges of the tape
v	DOWN	Increases cell pointer's Y value by I	I (unchanged)	This moves the current cell down by I. Cell positions wrap at the edges of the tape
/	PUSH	Pushes I to the top of the stack	The new stack size
|	READ	No effect on state	Returns the value on the stack I positions deep. If the stack is empty, returns the current cell value instead	|0 returns the topmost stack element. Stack positions wrap around, so |-1 returns the bottom element of the stack.
\	POP	Removes the value on the stack I positions deep. If the stack is empty, there is no effect.	Returns the removed value. If the stack is empty, returns the current cell value instead	\0 removes and returns the topmost stack element. Stack positions wrap around, so \-1 removes and returns the bottom element of the stack.
;	DEBUG	Writes debug information about the current state to standard output. No other effect on state	I (unchanged)	What is output is up to the implementation. F# implementation outputs value of various state variables, the command fragment passed as an argument, and then waits for Console.ReadLine() before proceeding

So the command <:?\0:

• Pops the top value from the stack (or returns the cell value if the stack is empty)
• Jumps ahead by that many commands IF the current cell value is positive, else 0
• Move the cell pointer to the left by the amount of commands jumped over
• Returns the amount of commands jumped over

After executing the command, that returned number is added to the cell that the cell pointer is now pointing to.