Pre-pre-block

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Pre-pre-block
x = 2, y = 3, rule = B3/S23 2o$bo$o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THUMBSIZE 3 GPS 1 AUTOSTART PAUSE 2 T 2 PAUSE 2 LOOP 3 ]]
Pattern type Miscellaneous
Number of cells 4
Bounding box 2×3
Discovered by Unknown
Year of discovery Unknown

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.

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]

x = 22, y = 18, rule = B3/S23 $obo$b2o$bo11$4bo$4b2o13b3o$3bobo13bo$20bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THUMBSIZE 2 Z 20 HEIGHT 480 GPS 10 AUTOSTART PAUSE 2 T 23 PAUSE 2 LOOP 60 ]]
(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.

x = 23, y = 20, rule = 23/3 10bo$10bo$10bo5$b2o17b2o$obo16b2o$2bo18bo$10bo$10bo$10bo5$b2o17b2o$obo 17bobo$2bo17bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THUMBSIZE 2 Z 20 HEIGHT 480 GPS 10 AUTOSTART PAUSE 2 T 24 PAUSE 2 T 25 PAUSE 2 LOOP 60 ]]
(click above to open LifeViewer)
RLE: here Plaintext: here

Notes

  1. 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.

References

  1. Robert Wainwright (September 1971). "Lifeline Volume 3". Lifeline page 6.

External links