evolve1d refacto, evolve2d repair

src/modules/core.js

@@ -1,23 +1,26 @@
 // core functions to generate initial states and evolve them
 
-// handles negative index and index bigger than its array length
-function guard(index, arrayLength) {
-  if (index > arrayLength - 1) return 0;
-  if (index < 0) return arrayLength - 1;
-  return index;
-}
+// get the next evolution of a 1D CA initial state
+// buggy BUT produces interesting results
+// function evolve1d(state, rules) {
+//   const sl = state.length - 1;
+//   return [
+//     rules[[state[sl - 1], state[sl], state[sl + 1]].join("")],
+//     ...state.map((_,x) => (rules[[state[x - 1], state[x], state[x + 1]].join("")])).slice(0, sl),
+//     rules[[state[0], state[1], state[2]].join("")]
+//   ]
+// }
 
 // get the next evolution of a 1D CA initial state
 function evolve1d(state, rules) {
-  function getCell(index) {
-    const safeIndex = guard(index, state.length);
-    return state[safeIndex];
-  }
-  const newState = state.map((_, x) => {
-    const cells = [getCell(x - 1), getCell(x), getCell(x + 1)];
-    return rules[cells.join("")];
-  });
-  return newState.map(Number);
+  const sl = state.length - 1;
+  const edge1 = [state[sl - 2], state[sl - 1], state[sl]].join("");
+  const edge2 = [state[0], state[1], state[2]].join("");
+  // normal case (3 neighbor cells)
+  const center = state
+    .map((_, x) => rules[[state[x - 1], state[x], state[x + 1]].join("")])
+    .slice(1, sl);
+  return [rules[edge1], ...center, rules[edge2]];
 }
 
 // create a 2D board from a 1D CA initial state
@@ -49,31 +52,6 @@ function createBoard(state, rules, max) {
   return board;
 }
 
-// Find the neighbor of a given cell in a 2D CA board
-function getCellNeighbors(board, cellCoordinates) {
-  const [x, y] = cellCoordinates;
-  const rowLength = board[0].length; // caca?
-
-  // handles board edges where the cell is missing neighbors
-  function getCell(xx, yy) {
-    const safeX = guard(xx, board.length);
-    const safeY = guard(yy, rowLength.length);
-    return board[safeX][safeY];
-  }
-
-  // the current cell is not included in the result
-  return [
-    getCell(x - 1, y - 1),
-    getCell(x, y - 1),
-    getCell(x + 1, y - 1),
-    getCell(x - 1, y),
-    getCell(x + 1, y),
-    getCell(x - 1, y + 1),
-    getCell(x, y + 1),
-    getCell(x + 1, y - 1),
-  ];
-}
-
 // Sums the value of a cell's neighbors
 function getNeighborsSum(cells) {
   return cells.reduce((cell, acc) => cell + acc, 0);
@@ -152,13 +130,31 @@ function overpopulationRules(cell, neighbors) {
 // get the next evolution of a 2D CA initial state
 // Rules : Moore neighborhood
 function evolve2d(board, rulesFn) {
-  return board.map((row, x) =>
-    row.map((cell, y) => {
-      const neighbors = getCellNeighbors(board, [x, y]);
+  const bh = board.length - 1;
+  const bw = board[0].length - 1;
+  return board.map((row, y) => {
+    // handle edges
+    const prow = y - 1 < 0 ? board[bh] : board[y - 1];
+    const nrow = y + 1 > bh ? board[0] : board[y + 1];
+    return row.map((cell, x) => {
+      // handle edges too
+      const pcell = x - 1 < 0 ? bw : x - 1;
+      const ncell = x + 1 > bw ? 0 : x + 1;
+      // the current cell is not included in the result
+      const neighbors = [
+        prow[pcell],
+        prow[x],
+        prow[ncell],
+        row[pcell],
+        row[ncell],
+        nrow[pcell],
+        nrow[x],
+        nrow[ncell],
+      ];
       const sum = getNeighborsSum(neighbors);
       return rulesFn(cell, sum);
-    })
-  );
+    });
+  });
 }
 
 function getDrawingValues(state, acc, cell) {