switch engine

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English

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Noun

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switch engine (plural switch engines)

  1. A switcher or shunter: a railroad locomotive used for shunting.
  2. (cellular automata) A particular methuselah in Conway's Game of Life that temporarily exhibits glide reflection symmetry while leaving debris behind, allowing for the construction of spaceships, puffers, and rakes.
    • 1990 May 17, David Moews, “Life questions”, in comp.theory.cell-automata[1] (Usenet):
      2. Is it possible to make the switch engine leave debris other than the normal 8 blocks/288 generations?
    • 1992 August 13, David Bell, “Spaceships in Conway's Life (Part 1)”, in comp.theory.cell-automata[2] (Usenet):
      He did this by placing a large number of switch engines together so as to eliminate all debris. His original ship required 13 switch engines, but his smaller one given here only uses 10 of them.
    • 2007 May 12, Dave Greene, “Wanted: 2D CA, "as complex" but "denser" than Life”, in comp.theory.cell-automata[3] (Usenet):
      The average random Life pattern settles down instead of exploding (if you ignore output gliders and spaceships). There are exceptional quadratic-growth cases, mostly involving switch engines, but most random patterns affect only their immediate area.