Pure glider generator
A pure glider generator (or simply glider generator) is a pattern that evolves into one or more gliders and nothing else. They are part of the cosmological classification of Life patterns. There was interest in this scheme early on, and within it on pure glider generators in particular (they were reported on quite frequently in the early issues of Lifeline, for example), but nowadays they are no longer considered important.
The 4-8-12 diamond and the bi-loaf[note 1] are two pure glider generators found by the Honeywell group in 1971. The former evolves into four gliders (one heading in each diagonal direction) in 15 generations, while the latter yields two after four ticks. Gliders from the bi-loaf run in opposite ways along the diagonal that is closest to the great axis of the pattern. E.g. when the great axis is NNE-SSW, the gliders' directions are northeast & southwest.