Within the context of still lifes, a string is a pattern with a connectivity graph of the shape 8>o-o-(…)-o<8 (ie. with a string of S2 cells stabilized by two "caps"). All string stlifes are primitive.
Any fuse body must terminate in a two-cell cap called hook, or join by a turn with another object for stability. Two commonly occurring four-cell terminations are tail, which can be analyzed as a turn + a degenerate 1-cell fuse + hook; and claw, which is a turn + degenerate length-1 boat. These are best treated as independant endings:
- The "fuse" inside a tail cannot be extended, if joined into a fuse of length > 2.
- A length-1 boat is not an object by itself and so any string terminated with a claw will be primitive, unlike strings terminated with a longer separate object.
There is also a way combine two parallel fuse bodies three lanes apart, using a turn (notation: u). Both fuses cannot be extended indefinitely; the only way to extend the more ahead one beyond 2 cells is to loop the still life back on itself: a loaf is an u2u3 loop, and a mango is an u3u3 loop. The 2nd fuse can also be replaced with a vessel. Two turns may be combined with a dummy fuse in-between to create a five-lane offset, in two ways. -u1u- is a trimino, while -u2u- is may be called kink.
While a string can be described using turns, hooks and fuse bodies alone, the severe restrictions on the placement of turns means their occurrences can largely be condensed into ___. The following grammar may be used to describe most primitive strings:
- h: hook
- L: tail (= h1u)
- C: claw (= B1u)
- T: trimino (= u1u)
- K: kink (= u2u)
A few still lifes can be described under this notation in two ways though: the simplest case is fuse with two tails, h1u2u1h, which can be condensed to either h1K1h or L2L. Similarly, h1u2u1u2u1h will be either h1K1K1h or L2T2L.
- 6 cells: snake (h2h)
- 7 cells: eater (h1C), long snake (h3h)
- 8 cells: hook with tail (h2L), shillelagh (h2C), canoe (c-h4h), long long snake (h4h)
- 9 cells: integral (C1C), long shillelagh (h3C)
- 10 cells: long integral (C2C), trans-fuse with two tails (L2L), long² shillelagh (h4C), cis shillelagh (c-h4C),