array_push($payload, $al + $ar); } elseif ($symbol == '-') { array_push($payload, $al - $ar); } elseif ($symbol == '*') { array_push($payload, $al * $ar); } elseif ($symbol == '/') { array_push($payload, $al / $ar); } } function DoEqual($symbol, $payload) { echo array_pop($payload) . "\n"; } function Error($symbol, $payload) { echo "This does not compute: {$symbol}\n"; } $stack = array(); $fsm = new FSM('INIT', $stack); $fsm->setDefaultTransition('INIT', 'Error'); $fsm->addTransitionAny('INIT', 'INIT'); $fsm->addTransition('=', 'INIT', 'INIT', 'DoEqual'); $fsm->addTransitions(range(0, 9), 'INIT', 'BUILDING_NUMBER', 'BeginBuildNumber'); $fsm->addTransitions(range(0, 9), 'BUILDING_NUMBER', 'BUILDING_NUMBER', 'BuildNumber'); $fsm->addTransition(' ', 'BUILDING_NUMBER', 'INIT', 'EndBuildNumber'); $fsm->addTransitions(array('+', '-', '*', '/'), 'INIT', 'INIT', 'DoOperator'); echo "Expression:\n"; $stdin = fopen('php://stdin', 'r'); $expression = rtrim(fgets($stdin)); $symbols = preg_split('//', $expression, -1, PREG_SPLIT_NO_EMPTY); $fsm->processList($symbols);