Dathanna

Dathanna (Irish for "colors") is an esoteric programming language for Apple II emulators.

Rationale

Most classic computers from the 1980s have emulators so old code can run on modern hardware. Many of these emulators support running as quickly as possible, often several orders of magnitude faster than the original machine. Dathanna takes advantage of this speed to make tolerable an implementation that would otherwise be far too slow on the original hardware.

Dathanna is featured in Chapter 16 of the book Strange Code: Esoteric Languages That Make Programming Fun Again (No Starch Press, 2022).

Language Description

Dathanna programs are constructed from pairs of colored blocks stacked one on top of the other. The top color specifies the command and the bottom a modifier for that command. Programs are arranged on the screen and execute from left to right, top to bottom.

Arithmetic operations use a stack with colors doing double-duty as commands or numbers. The stack supports floating-point numbers but only the integers 0 through 15 can be pushed on the stack directly.

Dathanna colors and numeric values

Commands

Commands are a top color with the lower color a modifier.

Value	Color	Top	Bottom
0	black	HALT	Terminate program (any)
1	magenta	PUSH	push number to top-of-stack (TOS) (any)
2	dark blue	INPUT	number to TOS (orange)
			character to TOS (light green)
3	purple	COMPARE	< (gray 1)
			<= (medium blue)
			> (light blue)
			>= (brown)
			= (orange)
			<> (gray 2)
			(r c -- ) branch (purple)
			(r c f -- ) if (aquamarine)
4	gray 1	STACK	dup (magenta)
			drop (dark blue)
			swap (purple)
			rot (gray 1)
			over (medium blue)
			nip (light blue)
7	light blue	PRINT	TOS as number (orange)
			TOS as character (light green)
9	orange	MATH	+ (black)
			- (magenta)
			* (dark blue)
			/ (purple)
			ˆ (dark green)
			sqrt (gray 1)
			sin (medium blue)
			cos (light blue)
			tan (brown)
			abs (orange)
			exp (gray 2)
			log (pink)
			int (light green)
			rnd (yellow)
			atn (aquamarine)
			mod (white)
12	light green	STORE	( v idx -- ) (any)
13	yellow	FETCH	( idx -- v) (any)
14	aquamarine	PUTV	TOS to var number (any)
15	white	GETV	var number to TOS (any)

Examples

Hello, world!

Random Pi

Gnome Sort

Computational class

Like Befunge-93, Dathanna programs are restricted to one screen. Therefore, Dathanna is not Turing complete.

Implementations

• Official interpreter, disk image, and documentation