Sunday, 25 January 2009

Brainf*** Interpreter in Redcode

Brainf*** is an esoteric programming language developed by Urban Müller. There are 8 instructions in brainf***:

<ltmove pointer left
>gtmove pointer right
+incincrement memory cell at pointer
-decdecrement memory cell at pointer
.outoutput a character from the cell at pointer
,ininput a character and store in cell at pointer
[opjump past matching ] if cell at pointer is 0
]cljump to matching [ if cell at pointer not 0

Brainf*** operates on an array of memory cells and has a pointer into the array. Each instruction translates directly into Redcode. Before executing the brainf*** program, the interpreter calculates and stores the offset for [ and ] to avoid repeated searching.

Here's the code:

        lt equ sub #1, ptr
gt equ add #1, ptr
inc equ add #1, @ptr
dec equ sub #1, @ptr
out equ sts @ptr, 0
in equ lds @ptr, 0
op equ jmz 0, @ptr
cl equ jmn 2, @ptr

org seek

ptr #0, #prog

find sne.a #2, *ptr
sub #1, count
sne.a #0, }ptr
jmp find, >count
count jmn find, #0

mov.a ptr, @ptr ptr, >ptr ptr, {ptr
sub.a ptr, *ptr

seek jmn.a seek, >ptr
jmn ptr, <ptr



John said...

The interpreter executes Erik Bosman's Quine in 860601 cycles.

Roy said...

Show off ;-)

(well done!)