Pre-pre-block
| Pre-pre-block | |||||||||
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| Pattern type | Still life component | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Number of cells | 4 | ||||||||
| Bounding box | 2 × 3 | ||||||||
| Discovered by | Unknown | ||||||||
| Year of discovery | Unknown | ||||||||
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Pre-pre-block (or hook[note 1]) is a tetraplet (i.e. a polyplet containing four cells). It is a common predecessor to the pre-block (and thus the block). It also appears in some period-2 oscillators, e.g. bipole and almosymmetric, and is the first extension of pre-block.
In some cases, the specific reasons for this being unknown, the pre-pre-block is also known as cape.
The pre-pre-pre-block is a parent of this which sees further use in still lifes.
As a synthetic intermediate
One notable aspect about this particular block grandparent is that it is a key intermediate in glider syntheses of lightweight spaceship and middleweight spaceship. Some earliest MWSS guns was constructed by Bill Gosper and Robert Wainwright in 1971, employing the following productive mechanism where gliders from the northwest and southwest create the pre-pre-block.[1]
| (click above to open LifeViewer) RLE: here Plaintext: here |
If the glider from the southeast can interact with the forming pre-pre-block one generation earlier, the result is an LWSS instead of an MWSS. However, this requires a different recipe, such as a glider colliding with a blinker.
| (click above to open LifeViewer) RLE: here Plaintext: here |
Notes
- ↑ The name "hook" is still used when naming some still lifes, such as hook with tail, where a tail stabilizes a pre-pre-block. However, by calling a disconnected part of a still life a hook, one may actually refer to an induction coil bookend; this latter terminology is being phased out as to avert confusion.
References
- ↑ Robert Wainwright (September 1971). Lifeline, vol 3, page 6.
External links
- Pre-pre-block at the Life Lexicon
- Hook at the Life Lexicon