public function evaluate()
{
$output = new Stack();
for ($i = 0; $i < count($this->tokens); $i++) {
$t = $this->tokens[$i];
if ($t->getType() == Token::TOKEN_NUMBER) {
$output->push($t->getValue());
} else {
if ($t->getType() == Token::TOKEN_VARIABLE) {
$name = $t->getName();
if (!isset($this->variables[$name])) {
throw new ExpressionException("No value has been set for the setVariable '" . $name . "'.");
}
$value = $this->variables[$name];
$output->push($value);
} else {
if ($t->getType() == Token::TOKEN_OPERATOR) {
$op = $t;
if ($output->size() < $op->getOperator()->getNumOperands()) {
throw new ExpressionException("Invalid number of operands available");
}
if ($op->getOperator()->getNumOperands() == 2) {
/* pop the operands and push the result of the operation */
$rightArg = $output->pop();
$leftArg = $output->pop();
$output->push($op->getOperator()->apply([$leftArg, $rightArg]));
} else {
if ($op->getOperator()->getNumOperands() == 1) {
/* pop the operand and push the result of the operation */
$arg = $output->pop();
$output->push($op->getOperator()->apply([$arg]));
}
}
} else {
if ($t->getType() == Token::TOKEN_FUNCTION) {
/** @var FunctionToken $func */
$func = $t;
if ($func->getFunction()->getNumArguments() > $func->getPassedArgumentCount()) {
throw new ExpressionException("Function " . $func->getFunction()->getName() . " requires at least " . $func->getFunction()->getNumArguments() . " arguments (" . $func->getPassedArgumentCount() . " passed)");
}
if ($output->size() < $func->getFunction()->getNumArguments()) {
throw new ExpressionException("Invalid number of arguments available");
}
/* collect the arguments from the stack */
$args = [];
for ($j = 0; $j < $func->getPassedArgumentCount(); $j++) {
$args[$j] = $output->pop();
}
$output->push($func->getFunction()->apply($this->reverseInPlace($args)));
}
}
}
}
}
if ($output->size() > 1) {
throw new ExpressionException("Invalid number of items on the output queue. Might be caused by an invalid number of arguments for a function.");
}
return $output->pop();
}
/**
* Convert a Set of tokens from infix to reverse polish notation
* @param string $expression the expression to convert
* @param array $userFunctions the custom functions used
* @param array $userOperators the custom operators used
* @param array $variableNames
* @return array of tokens containing the result
*/
public static function convertToRPN($expression, $userFunctions, $userOperators, $variableNames)
{
$stack = new Stack();
$functionStack = new Stack();
$output = [];
$tokenizer = new Tokenizer($expression, $userFunctions, $userOperators, $variableNames);
while ($tokenizer->hasNext()) {
$token = $tokenizer->nextToken();
switch ($token->getType()) {
case Token::TOKEN_NUMBER:
case Token::TOKEN_VARIABLE:
$output[] = $token;
break;
case Token::TOKEN_FUNCTION:
$stack->add($token);
$functionStack->add($token);
break;
case Token::TOKEN_SEPARATOR:
// store argument count, easier than easy
if (!$functionStack->isEmpty()) {
$functionToken = $functionStack->peek();
$functionToken->incPassedArgumentCount();
}
while (!$stack->isEmpty() && $stack->peek()->getType() != Token::TOKEN_PARENTHESES_OPEN) {
$output[] = $stack->pop();
}
if ($stack->isEmpty() || $stack->peek()->getType() != Token::TOKEN_PARENTHESES_OPEN) {
throw new ExpressionException("Misplaced function separator ',' or mismatched parentheses");
}
break;
case Token::TOKEN_OPERATOR:
while (!$stack->isEmpty() && $stack->peek()->getType() == Token::TOKEN_OPERATOR) {
$o1 = $token;
$o2 = $stack->peek();
if ($o1->getOperator()->getNumOperands() == 1 && $o2->getOperator()->getNumOperands() == 2) {
break;
} else {
if ($o1->getOperator()->isLeftAssociative() && $o1->getOperator()->getPrecedence() <= $o2->getOperator()->getPrecedence() || $o1->getOperator()->getPrecedence() < $o2->getOperator()->getPrecedence()) {
$output[] = $stack->pop();
} else {
break;
}
}
}
$stack->push($token);
break;
case Token::TOKEN_PARENTHESES_OPEN:
$stack->push($token);
break;
case Token::TOKEN_PARENTHESES_CLOSE:
while ($stack->peek()->getType() != Token::TOKEN_PARENTHESES_OPEN) {
$output[] = $stack->pop();
}
$stack->pop();
if (!$stack->isEmpty() && $stack->peek()->getType() == Token::TOKEN_FUNCTION) {
$output[] = $stack->pop();
$functionStack->pop();
}
break;
default:
throw new ExpressionException("Unknown Token type encountered. This should not happen");
}
}
while (!$stack->isEmpty()) {
$t = $stack->pop();
if ($t->getType() == Token::TOKEN_PARENTHESES_CLOSE || $t->getType() == Token::TOKEN_PARENTHESES_OPEN) {
throw new ExpressionException("Mismatched parentheses detected. Please check the expression");
} else {
$output[] = $t;
}
}
return $output;
}