Viewing file:  rpn.php (1.58 KB) -rw-r--r--
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<?php
require_once 'FSM.php';
function BeginBuildNumber($symbol, $payload)
{
array_push($payload, $symbol);
}
function BuildNumber($symbol, $payload)
{
$n = array_pop($payload);
$n = $n . $symbol;
array_push($payload, $n);
}
function EndBuildNumber($symbol, $payload)
{
$n = array_pop($payload);
array_push($payload, (int)$n);
}
function DoOperator($symbol, $payload)
{
$ar = array_pop($payload);
$al = array_pop($payload);
if ($symbol == '+') {
array_push($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);
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