/**
* @link http://php.net/manual/en/iterator.rewind.php
* @return void
*/
function rewind()
{
$this->stack = new LinkedStack();
$this->pushLeft($this->root);
if (!$this->stack->isEmpty()) {
$this->node = $this->stack->last();
$this->key = 0;
}
}
/**
* @link http://php.net/manual/en/iterator.next.php
* @return void
*/
function next()
{
/**
* @var BinaryTree $node
*/
$node = $this->stack->pop();
$this->pushIfNotNull('right', $node);
$this->pushIfNotNull('left', $node);
if ($this->stack->isEmpty()) {
$this->value = $this->key = null;
return;
}
$this->value = $this->stack->last();
$this->key++;
}
private function next_right()
{
$right = $this->value->right();
if ($right !== null && !$this->stack->isEmpty() && $right === $this->stack->last()) {
$this->stack->pop();
$this->next_push($right);
} else {
$this->next_set();
}
}
public function nfx($expr)
{
$index = 0;
$stack = new Stack();
$output = array();
// postfix form of expression, to be passed to pfx()
// $expr = trim(strtolower($expr));
$expr = trim($expr);
$ops = array('+', '-', '*', '/', '^', '_');
$ops_r = array('+' => 0, '-' => 0, '*' => 0, '/' => 0, '^' => 1);
// right-associative operator?
$ops_p = array('+' => 0, '-' => 0, '*' => 1, '/' => 1, '_' => 1, '^' => 2);
// operator precedence
$expecting_op = false;
// we use this in syntax-checking the expression
// and determining when a - is a negation
if (preg_match("/[^\\w\\s+*^\\/()\\.,-]/", $expr, $matches)) {
// make sure the characters are all good
return $this->trigger("illegal character '{$matches[0]}'");
}
while (1) {
// 1 Infinite Loop ;)
$op = substr($expr, $index, 1);
// get the first character at the current index
// find out if we're currently at the beginning of a number/variable/function/parenthesis/operand
$ex = preg_match('/^([A-Za-z]\\w*\\(?|\\d+(?:\\.\\d*)?|\\.\\d+|\\()/', substr($expr, $index), $match);
//===============
if ($op == '-' and !$expecting_op) {
// is it a negation instead of a minus?
$stack->push('_');
// put a negation on the stack
$index++;
} elseif ($op == '_') {
// we have to explicitly deny this, because it's legal on the stack
return $this->trigger("illegal character '_'");
// but not in the input expression
//===============
} elseif ((in_array($op, $ops) or $ex) and $expecting_op) {
// are we putting an operator on the stack?
if ($ex) {
// are we expecting an operator but have a number/variable/function/opening parethesis?
$op = '*';
$index--;
// it's an implicit multiplication
}
// heart of the algorithm:
while ($stack->count > 0 and $o2 = $stack->last() and in_array($o2, $ops) and $ops_r[$op] ? $ops_p[$op] < $ops_p[$o2] : $ops_p[$op] <= $ops_p[$o2]) {
$output[] = $stack->pop();
// pop stuff off the stack into the output
}
// many thanks: http://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail
$stack->push($op);
// finally put OUR operator onto the stack
$index++;
$expecting_op = false;
//===============
} elseif ($op == ')' and $expecting_op) {
// ready to close a parenthesis?
while (($o2 = $stack->pop()) != '(') {
// pop off the stack back to the last (
if (is_null($o2)) {
return $this->trigger("unexpected ')'");
} else {
$output[] = $o2;
}
}
if (preg_match("/^([A-Za-z]\\w*)\\(\$/", $stack->last(2), $matches)) {
// did we just close a function?
$fnn = $matches[1];
// get the function name
$arg_count = $stack->pop();
// see how many arguments there were (cleverly stored on the stack, thank you)
$output[] = $stack->pop();
// pop the function and push onto the output
if (in_array($fnn, $this->fb)) {
// check the argument count
if ($arg_count > 1) {
return $this->trigger("too many arguments ({$arg_count} given, 1 expected)");
}
} elseif (array_key_exists($fnn, $this->f)) {
if ($arg_count != count($this->f[$fnn]['args'])) {
return $this->trigger("wrong number of arguments ({$arg_count} given, " . count($this->f[$fnn]['args']) . " expected)");
}
} else {
// did we somehow push a non-function on the stack? this should never happen
return $this->trigger("internal error");
}
}
$index++;
//===============
} elseif ($op == ',' and $expecting_op) {
// did we just finish a function argument?
while (($o2 = $stack->pop()) != '(') {
if (is_null($o2)) {
return $this->trigger("unexpected ','");
} else {
$output[] = $o2;
}
// pop the argument expression stuff and push onto the output
}
// make sure there was a function
if (!preg_match("/^([A-Za-z]\\w*)\\(\$/", $stack->last(2), $matches)) {
return $this->trigger("unexpected ','");
}
$stack->push($stack->pop() + 1);
// increment the argument count
$stack->push('(');
// put the ( back on, we'll need to pop back to it again
$index++;
$expecting_op = false;
//===============
} elseif ($op == '(' and !$expecting_op) {
$stack->push('(');
// that was easy
$index++;
$allow_neg = true;
//===============
} elseif ($ex and !$expecting_op) {
// do we now have a function/variable/number?
$expecting_op = true;
$val = $match[1];
if (preg_match("/^([A-Za-z]\\w*)\\(\$/", $val, $matches)) {
// may be func, or variable w/ implicit multiplication against parentheses...
if (in_array($matches[1], $this->fb) or array_key_exists($matches[1], $this->f)) {
// it's a func
$stack->push($val);
$stack->push(1);
$stack->push('(');
$expecting_op = false;
} else {
// it's a var w/ implicit multiplication
$val = $matches[1];
$output[] = $val;
}
} else {
// it's a plain old var or num
$output[] = $val;
}
$index += strlen($val);
//===============
} elseif ($op == ')') {
// miscellaneous error checking
return $this->trigger("unexpected ')'");
} elseif (in_array($op, $ops) and !$expecting_op) {
return $this->trigger("unexpected operator '{$op}'");
} else {
// I don't even want to know what you did to get here
return $this->trigger("an unexpected error occured");
}
if ($index == strlen($expr)) {
if (in_array($op, $ops)) {
// did we end with an operator? bad.
return $this->trigger("operator '{$op}' lacks operand");
} else {
break;
}
}
while (substr($expr, $index, 1) == ' ') {
// step the index past whitespace (pretty much turns whitespace
$index++;
// into implicit multiplication if no operator is there)
}
}
while (!is_null($op = $stack->pop())) {
// pop everything off the stack and push onto output
if ($op == '(') {
return $this->trigger("expecting ')'");
}
// if there are (s on the stack, ()s were unbalanced
$output[] = $op;
}
return $output;
}
} else {
echo "stack is empty";
}
}
public function isEmpty()
{
if ($this->index == -1) {
return true;
} else {
return false;
}
}
public function first()
{
echo $this->stackArray[$this->index];
}
public function last()
{
echo $this->stackArray[0];
}
}
$newStack = new Stack();
$newStack->push(2);
$newStack->push(6);
$newStack->pop();
$newStack->pop();
$newStack->pop();
$newStack->isEmpty();
$newStack->first();
$newStack->last();
$newStack->getElement(1);
$this->index--;
return $element;
}
echo "There is no element in the quee array";
}
public function isEmpty()
{
if ($this->index == -1) {
return true;
} else {
return false;
}
}
public function first()
{
return $this->queArray[$this->index];
}
public function last()
{
return $this->queArray[0];
}
}
$muy = new Stack(array(3, 4, 7));
$myStack = new Stack();
$myStack->push(1);
$myStack->push(4);
echo $myStack->first(), "<br>";
echo $myStack->last(), "<br>";
echo $myStack->pop(), "<br>";
echo $myStack->pop(), "<br>";
$myStack->pop();
