Home Befunge
News News
Befunge Befunge
   - Programs
   - Compilers
   - Interpreters
   - Documentation

Doom Doom
Inform Inform
Quake Quake
Misc Misc
Links Links
Contact Contact

Befunge 'troll' programs

Sometime around October/November 2002, I decided to write a self-replicating Befunge program. Not a quine, but a program which copies itself from one area of fungespace to another. The result was the following series of 'trolls'. I've called them trolls because at the time I was sure that 'troll' was the name of one of the programs in an age old RISC OS port of CoreWars. It turns out I was wrong, but the name stuck.

  • troll.bf (413 bytes)
    The original troll, which can copy itself to one of six locations in befunge-93 space. It's slow, but illustrates the key processes in a multi-dimensional troll implementation:
    1. Deciding where to move
    2. Copying ourself there
    3. Setting up a route for the IP to travel along in order to reach the new copy

    The only real problem with it is that it stores data at a fixed location (the top-left corner of funge space); i.e. it doesn't modify itself to read/write variables inside the active copy.
  • troll2.bf (352 bytes)
    Troll1 with all the 'garbage' removed.
  • troll3.bf (384 bytes)
    A rewrite of the troll. It's still only able to travel to 6 locations but is a faster, smaller, and better implementation overall.
  • troll4.bf (152 bytes)
    My first attempt at a 1-dimensional troll. It's still a befunge program, and works by copying itself down through fungespace one cell at a time. It's fairly slow due to the stringmode backwards-jump technique employed, and travel from copy to copy is entirely random. If another program was inserted then it may well end up running that instead.
  • troll5.bf (157 bytes)
    Another 1-dimensional troll, this time it moves properly between the different copies (i.e. from one to the next).
  • troll6.bf
    Unreleased, unfinished prototype for troll7.
  • troll7.bf (1,733 bytes)
    A 2D troll which erases the original after making a copy! Fitting it into the 26x12 space was a bit tricky, but I got there in the end. After the code there are a few notes on how it works. Also take a look at this colour-coded picture to make understanding the code easier.
  • troll8.bf (320 bytes)
    A quick attempt at a Befunge-98 troll. It'll copy itself to a random location in fungespace (right up to the +/-2^31 limit), and partially erase the old copy. At some point I'll probably write a new one which erases itself properly. Might even try trefunge. Prints out a '1' every time it's about to copy itself so you can tell how fast it's going (Or when it's crashed).

Page last modified 03/03/2005