(a) temporarily destroying some still life, and going back and replacing it later, or
(b) creating an unwanted still life as a byproduct of a useful reaction, and going back and removing it later.
Generally (b) is easier than (a), since most simple still lifes can be annihilated by a single glider on the correct lane -- maybe with the help of a catalyst, but with few or no timing constraints. If a period-2 byproduct (most commonly a blinker) has to be modified or removed, this usually cuts in half the allowable spacetime locations for cleanup gliders, but still leaves a very wide search space.
So this kind of repair just means routing a Herschel to any one of twenty-plus known Herschel-to-glider converters, anywhere along the target glider lane, with a wide range of timings (usually the quicker the better). With this many degrees of freedom, a Hersrch search can generally find a fairly compact solution.
-- Compact as these things go, that is! With a choice of 17 conduits in the basic set, a string of (say) three to five conduits will often be enough to put a glider on the correct lane, without having to wander off too far in the wrong direction -- unless the glider lane is too close to the input Herschel. A target area at least fifty cells away from the input Herschel should usually allow a clean connection to be made. I'll work on some rough coverage graphs for a separate posting.
The basic idea behind a staged-recovery construction is that it's often possible to quickly make a repair, even a difficult repair -- say, rebuilding a loaf used to reflect an incoming glider, as shown below -- at the cost of some minor damage to the repairing circuitry. If the damage itself can be repaired relatively quickly and easily, the result is a somewhat more complex circuit that can recover more quickly overall -- if the initial part of the circuit is triggered again, the damaged area can often be repaired before the next signal reaches it.
recovery time is 1696 ticks, but the pattern does not become
stable again for 2234 ticks.
The primary use of the staged-recovery idea in the transmitter is in the northeast circuit, which asynchronously rebuilds a beehive and sends in a glider to reset the beginning of the 2c/3 wire after the signal is sent. The pattern could be rearranged to trigger this circuit considerably faster -- or even *before* the main trigger signal arrives (in which case the quiescent state of the transmitter would not include a beehive).
Here's a Python script that builds a complete P1 Heisenburp device from its component parts. The above screenshot shows what it looks like in Golly 1.1. It can also take advantage of the new multi-layer functionality in Golly 1.2. In multi-layer mode, the script produces a screen something like this:
Update: The latest version of this script is now included as Scripts/heisenburp.py in the Golly 1.2 release distribution.