The vimscript (and Haskell) presented at the Boston Vim meetup, showi…

…ng Conway's Game of Life.

gameOfLife.hs

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+import Data.Maybe
+
+data Cell = Alive | Dead deriving (Eq, Show)
+
+tick board = rowsTick 0 board board
+
+rowsTick _ [] _ = []
+rowsTick rowNumber (row:rows) board =
+  (rowTick row board rowNumber 0):(rowsTick (rowNumber+1) rows board)
+
+rowTick [] _ _ _ = []
+rowTick (cell:cells) board rowNumber columnNumber =
+  tickedCell:(rowTick cells board rowNumber (columnNumber+1))
+  where tickedCell = cellTick cell board rowNumber columnNumber
+
+cellTick cell board rowNumber columnNumber =
+  transition cell $ liveNeighborsCount board rowNumber columnNumber
+
+liveNeighborsCount board rowNumber columnNumber =
+  length $ filter (Alive==) neighboringCells
+  where neighboringCells = [
+          board `at` (rowNumber-1,columnNumber-1),
+          board `at` (rowNumber-1,columnNumber),
+          board `at` (rowNumber-1,columnNumber+1),
+          board `at` (rowNumber, columnNumber-1),
+          board `at` (rowNumber, columnNumber+1),
+          board `at` (rowNumber+1, columnNumber-1),
+          board `at` (rowNumber+1, columnNumber),
+          board `at` (rowNumber+1, columnNumber+1)]
+
+transition Alive 2 = Alive
+transition Alive 3 = Alive
+transition Dead  3 = Alive
+transition _     _ = Dead
+
+at board (rowNumber, columnNumber)
+  | rowNumber < 0 || columnNumber < 0 = Dead
+  | otherwise = maybe Dead id foundCell
+    where
+      foundCell =
+        (listToMaybe $ drop rowNumber board) >>=
+          listToMaybe . drop columnNumber
+
+
+inputBoard = [
+  [Alive,Alive,Dead ,Dead ]
+ ,[Dead ,Alive,Dead ,Dead ]
+ ,[Alive,Alive,Dead ,Alive]
+ ,[Dead ,Dead ,Dead ,Dead ]
+  ]
+
+outputBoard = [
+  [Alive,Alive,Dead ,Dead ]
+ ,[Dead ,Dead ,Dead ,Dead ]
+ ,[Alive,Alive,Alive,Dead ]
+ ,[Dead ,Dead ,Dead ,Dead ]
+  ]
+
+main = putStrLn $ show $ tick inputBoard == outputBoard

game_of_life.vim

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+function! Transition(cell, numberOfLiveNeighbors)
+  if a:cell == "*" && (a:numberOfLiveNeighbors == 2 || a:numberOfLiveNeighbors == 3)
+    return "*"
+  elseif a:cell == "o" && a:numberOfLiveNeighbors == 3
+    return "*"
+  else
+    return "o"
+  endif
+endfunction
+
+function! At(matrix, x, y)
+  if a:x < 0 || a:y < 0
+    return "o"
+  else
+    return get(get(a:matrix, a:x, []), a:y, "o")
+  endif
+endfunction
+
+function! NeighboringCells(board, x, y)
+  return [ At(a:board, a:y-1, a:x-1), At(a:board, a:y-1, a:x), At(a:board, a:y-1, a:x+1), At(a:board, a:y, a:x-1), At(a:board, a:y, a:x+1), At(a:board, a:y+1, a:x-1), At(a:board, a:y+1, a:x), At(a:board, a:y+1, a:x+1) ]
+endfunction
+
+function! LiveNeighborsCount(board, x, y)
+  let l:neighbors = NeighboringCells(a:board, a:x, a:y)
+  return count(l:neighbors, "*")
+endfunction
+
+function! CellTick(cell, board, x, y)
+  let l:neighborsCount = LiveNeighborsCount(a:board, a:x, a:y)
+  return Transition(a:cell, l:neighborsCount)
+endfunction
+
+function! RowTick(row, board, x, y)
+  if a:row == []
+    return []
+  else
+    let l:cell = a:row[0]
+    let l:cells = a:row[1:]
+    let l:transitionedCell = CellTick(l:cell, a:board, a:x, a:y)
+    return [l:transitionedCell] + RowTick(l:cells, a:board, a:x+1, a:y)
+  endif
+endfunction
+
+function! RowsTick(y, rs, board)
+  if a:rs == []
+    return []
+  else
+    let l:row = a:rs[0]
+    let l:rows = a:rs[1:]
+    let l:transitionedRow = RowTick(l:row, a:board, 0, a:y)
+    return [l:transitionedRow] + RowsTick(a:y+1, l:rows, a:board)
+  endif
+endfunction
+
+function! Tick(board)
+  return RowsTick(0, a:board, a:board)
+endfunction
+
+function! UITick()
+  let l:board = []
+  for unparsedRow in getbufline(bufnr('%'), 1, '$')
+    let l:parsedRow = split(unparsedRow, ' ')
+    let l:board = add(l:board, l:parsedRow)
+  endfor
+
+  let l:nextBoard = Tick(l:board)
+
+  let l:nextBuffer = []
+  for nextRow in l:nextBoard
+    let l:nextLine = join(nextRow, ' ')
+    let l:nextBuffer = add(l:nextBuffer, l:nextLine)
+  endfor
+
+  normal! ggdG
+  exe "normal! i".join(l:nextBuffer, "\<cr>")."\<esc>"
+endfunction
+
+function! RunGameOfLife()
+  while 1
+    call UITick()
+    redraw
+    sleep 1
+  endwhile
+endfunction

game_of_life_test.vim

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+source test_unit.vim
+source game_of_life.vim
+
+call AssertEqual(Transition("*", 2), "*" )
+call AssertEqual(Transition("*", 3), "*" )
+call AssertEqual(Transition("o", 3), "*" )
+call AssertEqual(Transition("*", 4), "o" )
+
+call AssertEqual(At([["a","b"],["c","d"]], 4, 5), "o")

test_unit.vim

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+function! AssertEqual(actual, expected)
+  if a:actual == a:expected
+    echon "."
+  else
+    echom "Expected " . a:expected . " but got " . a:actual
+  end
+endfunction