Grin
| Grin | |||||||
| View static image | |||||||
| Pattern type | Miscellaneous | ||||||
|---|---|---|---|---|---|---|---|
| Number of cells | 4 | ||||||
| Bounding box | 4 × 2 | ||||||
| Discovered by | Unknown | ||||||
| Year of discovery | 1970 | ||||||
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- This article is about the block parent. For the oscillator, see Smiley.
Grin is a common parent of the block. Its name derives from the Cheshire cat, an 18-cell six-tick grin predecessor credited to C. R. Tompkins that appeared both in Scientific American[1] and in Winning Ways.
| Cheshire cat, leaving a block as its pawprint (click above to open LifeViewer) RLE: here Plaintext: here |
The grin can be forced to be stable with minor modifications. Two cells can transform it into a beehive, and three into a loaf. Two grins can be combined into either a pond or mango. The grin is not usually considered a still life component, however, since stabilisations tend to be more invasive than those of induction coils, tails and other objects.
Catalysis
Grin can be used to convert a beehive into a block, while turning into a block. Coe's p8 is most commonly used for this reaction, however 55P23 can also be used. The catalysis is not dependent on period as it only begins when a grin forms. This is exploited in p8 glider reflector and HRx74B.
Grin can also be detected and turned with a grin reagent or eater bridge eater. While eater bridge eater has a lower recovery time, drifters are known for grin reagent that can be used to interact with other objects, like a loading dock. This is exploited in 30P6.1, p8 glider reflector, 65P48 and 103P69.
| p8 glider reflector, highlighting both types of grin catalysis (click above to open LifeViewer) RLE: here Plaintext: here |
In other rules
Grin is a common photon (a lightspeed spaceship) in many Life-like cellular automata, for example Seeds and Live Free or Die. It is the third most common spaceship in the former, where it is known as moon. It works in 212 outer-totalistic rules (one sixty-fourth of all OT rules), from B2/S to B45678/S0345678, as well as 294 isotropic non-totalistic rules (one eighth), from B2ae/S to B23-j45678/S01e2-k345678.
The pattern also appears as a c/2 orthogonal spaceship in some B0 rules such as B0123/S6, interestingly keeping the same appearance in all phases.
See also
References
- ↑ Gardner, Martin (February 1971), "On cellular automata, self-reproduction, the Garden of Eden and the game 'life'", Scientific American 224 (2): 115–116
External links
- Grin at the Life Lexicon
- Cheshire cat at the Life Lexicon
- Seeds (B2/S) at David Eppstein's Glider Database
- Moon (rule b2s) at Adam P. Goucher's Catagolue