takeStep method
Take one step in the life of the world.
Implementation
void takeStep(Evolver e) {
final newCells = List<bool>.filled(nRows * nCols, false);
for (var i = 0; i < nRows; i++) {
for (var j = 0; j < nCols; j++) {
newCells[index(i, j)] = e.aliveAtNextStep(this, i, j);
}
}
_cells.setAll(0, newCells);
}