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23 lines
1.0 KiB
APL
23 lines
1.0 KiB
APL
⍝ Conway's Game of Life — toroidal one-liner
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⍝
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⍝ The classic Roger Hui formulation:
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⍝ life ← {⊃1 ⍵ ∨.∧ 3 4 = +/ +/ ¯1 0 1 ∘.⊖ ¯1 0 1 ⌽¨ ⊂⍵}
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⍝
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⍝ Read right-to-left:
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⍝ ⊂⍵ : enclose the board (so it's a single scalar item)
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⍝ ¯1 0 1 ⌽¨ ⊂⍵ : produce 3 horizontally-shifted copies
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⍝ ¯1 0 1 ∘.⊖ … : outer-product with vertical shifts → 3×3 = 9 shifts
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⍝ +/ +/ … : sum the 9 boards element-wise → neighbor-count + self
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⍝ 3 4 = … : boolean — count is exactly 3 or exactly 4
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⍝ 1 ⍵ ∨.∧ … : "alive next" iff (count=3) or (alive AND count=4)
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⍝ ⊃ … : disclose back to a 2D board
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⍝
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⍝ Rules in plain language:
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⍝ - dead cell + 3 live neighbors → born
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⍝ - live cell + 2 or 3 live neighbors → survives
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⍝ - all else → dies
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⍝
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⍝ Toroidal: edges wrap (rotate is cyclic).
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life ← {⊃1 ⍵ ∨.∧ 3 4 = +/ +/ ¯1 0 1 ∘.⊖ ¯1 0 1 ⌽¨ ⊂⍵}
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