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<?php
require_once('Destructable.php');
class Scope extends Destructable {
protected $_parent;
protected $definitions = array();
protected $assignments = array();
public function __destruct() {
$this->mem_flush('_parent', 'definitions', 'assignments');
}
/**
* Turns a name symbol into a variable symbol
*
* @param Symbol $symbol A name object occurring in the current scope
*/
public function define(&$symbol) {
if ($token = $this->definitions[$symbol->value] && $token->reserved) {
throw new Exception("Already defined: {$symbol->value}");
}
$this->definitions[$symbol->value] = $symbol;
$symbol->reserved = FALSE;
$symbol->nud = 'nud_itself';
$symbol->led = NULL;
$symbol->std = NULL;
$symbol->lbp = 0;
$symbol->scope = $this;
$symbol->global_scope = empty($this->_parent);
return $symbol;
}
/**
* Mark an assignment made in the current scope between two symbols
*
* @param Symbol $to_expression The expression $expression is assigned to
* @param Symbol $expression The expression being assigned
*/
public function assignment($to_expression, $expression) {
// Only let through assignments to actual lookups (foo or foo.bar.baz)
// where the assignment is also a lookup, or an object (which may contain lookups)
if (is_object($to_expression) && $to_expression->is_lookup()) {
if ($this !== $to_expression->scope) {
// The assignment might be referencing a higher scope (e.g. without var)
return $to_expression->scope->assignment($to_expression, $expression);
}
$this->assignments[$to_expression->value] = array();
$expressions = array($expression);
if ($possibilities = $this->possibilities($expression)) {
$expressions = $possibilities;
}
foreach ($expressions as $expression) {
if (is_object($expression) && ($expression->is_lookup() || $expression->id == '{')) {
$this->assignments[$to_expression->value][] = $expression;
}
}
}
}
protected function possibilities($symbol, $possibilities=array()) {
$symbols = $symbol;
if (!is_array($symbols)) {
$symbols = array($symbols);
}
foreach ($symbols as $symbol) {
if (is_array($symbol)) {
$possibilities = $this->possibilities($symbol, $possibilities);
}
elseif ($symbol->is_option()) {
$firsts = $symbol->first;
if (!is_array($firsts)) {
$firsts = array($firsts);
}
foreach ($firsts as $first) {
if (is_array($first)) {
$possibilities = $this->possibilities($first, $possibilities);
}
elseif ($first->possible_variable()) {
$possibilities[] = $first;
}
}
$seconds = $symbol->second;
if (!is_array($seconds)) {
$seconds = array($seconds);
}
foreach ($seconds as $second) {
if (is_array($second) || $second->is_option()) {
$possibilities = $this->possibilities($second, $possibilities);
}
elseif ($second->possible_variable()) {
$possibilities[] = $second;
}
}
}
}
return $possibilities;
}
public function assigned($variable, $as_array=FALSE) {
if (isset($this->assignments[$variable])) {
return $as_array ? $this->assignments[$variable] : $this->assignments[$variable][0];
}
if (isset($this->parent)) {
return $this->_parent->assigned($variable, $as_array);
}
}
/**
* Sets the current scope's parent
*
* @param Scope $parent
*/
public function setParent($parent) {
if ($parent instanceof Scope) {
return ($this->_parent = $parent);
}
}
/**
* Returns the current parent
*/
public function parent() {
// This is how pop() will work as well
return $this->_parent;
}
public function definition($name) {
return $this->definitions[$name];
}
/**
* Tries to look up through each scope
* to find a symbol with the same name
* and returns the global symbol or empty
* (name) symbol instead
*/
public function find ($name, $symbol_table) {
if ($symbol_table[$name]) {
return clone $symbol_table[$name];
}
$scope = $this;
while (1) {
if ($symbol = $scope->definition($name)) {
return clone $symbol;
}
if (!$scope->parent()) {
if (array_key_exists($name, $symbol_table)) {
return $symbol_table[$name];
}
$symbol = $symbol_table['(name)'];
$s = clone $symbol;
$s->global_scope = TRUE;
$s->reserved = FALSE;
$s->nud = 'nud_itself';
$s->led = NULL;
$s->std = NULL;
$s->lbp = 0;
$s->scope = $scope;
return $s;
}
$scope = $scope->parent();
}
}
/**
* Marks a variable symbol as being reserved in the current scope
*
* @param Symbol @symbol The variable symbol to mark reserved
*/
public function reserve($symbol) {
if ($symbol->arity != 'name' || $symbol->reserved) {
return;
}
if ($token = $this->definitions[$symbol->value]) {
if ($token->reserved) {
$symbol->reserved = TRUE;
if (!$this->parent()) {
$symbol->global_scope = TRUE;
}
return;
}
if ($token->arity == 'name') {
throw new Exception("Already defined: {$symbol->value}");
}
}
$symbol->reserved = TRUE;
if (!$this->parent()) {
$symbol->global_scope = TRUE;
}
$this->definitions[$symbol->value] = $symbol;
}
}
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