In cellular automata such as Conway's Game of Life, a breeder is a pattern that exhibits quadratic growth, by generating multiple copies of a secondary pattern, each of which then generates multiple copies of a tertiary pattern.
Breeders can be classed by the relative motion of the patterns. The classes are denoted by three-letter codes, which denote whether the primary, secondary and tertiary elements respectively are moving (M) or stationary (S). The four basic types are:
- SMM – A gun that fires out rakes.
- MSM – A puffer that leaves guns in its wake.
- MMS – A rake that fires out puffers.
- MMM – A rake that fires out more rakes, such that there are no stationary elements.
A spacefiller (which also undergoes quadratic growth) may be thought of as a fifth class of breeder. However it differs from a true breeder in that it expands a single island of cells, rather than creating independent objects.
- "Breeder – from Eric Weisstein's Treasure Trove of Life C.A." Retrieved 2008-11-01.