Tub

Tub
x = 3, y = 3, rule = B3/S23 bo$obo$bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C Still life
View static image
Pattern type	Strict still life
Number of cells	4
Bounding box	3×3
Frequency class	5.0
Discovered by	JHC group
Year of discovery	1970
Rules Outer-totalistic rules B/S2 – B35678/S012345678 Important rules Conway Life, HighLife # of rules 213 = 8192 Isotropic rules B/S2c – B2-e34-e5678/S012345678
Glider synthesis Fewest gliders 3 Catagolue-generated RLE tub_synth.rle Uploaded synthesis RLE tub_synth.rle
Pattern files Plaintext tub.cells RLE tub.rle
Identifiers apgcode xs4_252 Pentadecathlon ID 4.2

The tub is one of only two 4-cell still lifes (the other being the block) and was discovered by the JHC group in 1970.

Adding an extra cell to one of the corners results in a boat, while adding two to opposite corners results in a ship. It can be seen as a long^-1 version of the barge.

The tub is useful as a simple induction coil for a row of 5 cells.

Uses in catalysis

Two mechanisms for a tub acting as an eater are known, though rarely applicable. An example of the former is the Eureka shuttle. The other mechanism involves the tub acting as a rock; an example is 5blink. This can be generalized to a large number of still lifes including a tub-like protrusion (e.g. boat, loaf, cis-very long hook with tail).

Commonness

Tub is the sixth most common still life on Adam P. Goucher's Catagolue, being less common than ship but more common than pond. Among all still lifes with 4 cells, it is the absolute least common, preceded by block. It is also the eighth most common object overall on Catagolue. The tub is the fifth most common still life in Achim Flammenkamp's census, being about a quarter as common as the boat but only slightly more common than the pond.

Occurrence

The honey farm sequence has a tub in the center in its intermediate stages. If the sequence is interrupted partway through, whether naturally or as part of a honey farm hassler, the tub will sometimes survive. In addition to the honey farm, a U-turner forms a temporary tub, and a semi-common predecessor of a lone tub is shown in the gallery below.

x = 5, y = 5, rule = B3/S23 2o$o3bo$2b2o2$2bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ GPS 4 THUMBSIZE 2 ]]

A predecessor of a semi-common diagonally symmetric sequence (one of whose phases is a quarter of a pulsar) that makes a lone tub (click above to open LifeViewer) RLE: here Plaintext: here

Glider synthesis

A convenient 3-glider recipe for a tub starts with a two-glider synthesis of a pond, which is later hit by a third glider only one half-diagonal away from passing unharmed; this reaction produces a tub on the edge of envelope. There is also a perpendicular 2-glider collision that produces a tub along with junks, leading to another two-stage synthesis at the same cost. Other 3-glider collisions that produce a clean tub are also known.

See also

• Tub with tail
• Tutorials/Catalyses — showing details of when catalysts, including tubs, can be used

External links

• Tub at the Life Lexicon

• Tub at Adam P. Goucher's Catagolue

• The 2 four-bit still-lifes at Mark D. Niemiec's Life Page