Langton Self-Reproducing Loop

DEFINITION

8 states, von Neumann neighbourhood, 219 transitions CNESW → C′
rotation symmetric; replication period 151 generations

NOTES

Von Neumann proved self-reproduction needs no magic with a machine of 29 states nobody could run; Codd cut it to 8; Langton cut the idea to its heart — a loop of sheathed wire holding its own description as a circulating tape of gene signals, copying itself into a daughter loop every 151 steps. The colony spreads until loops run out of room, and the interior ones, unable to reproduce, retire into stillness: the growth leaves a coral of dead loops behind the living frontier, which Langton pointed to as the interesting part. The 219-rule table is carried as data, exactly as printed, and the same table drives both engines.

PROVENANCE

Origin

C. G. Langton, "Self-reproduction in cellular automata", Physica D 10(1–2), 1984, 135–144

Table

The transition table is Table 1 of the paper, via the Sayama–Bachmutsky transcription that Golly distributes — the table is the mathematics, carried as data the way sprott carries his codes; no library code runs here

Standing

Public domain automaton. No patent

Constants

The initial loop is the 86-cell configuration from the paper, placed and turned by seed — the table is rotation symmetric, so a turned loop runs identically turned

Source

doi:10.1016/0167-2789(84)90256-2