Added function to rebuild the original expression

parser.php

@@ -42,6 +42,31 @@ class ElementInstance {
  return implode('', $pieces);
  }
 
+ public function getRepresentation() {
+ static $stack_depth = 0; global $STACK_LIMIT;
+ if (++$stack_depth > $STACK_LIMIT) {
+ throw new RuntimeException('Stack limit exceeded.');
+ }
+ try {
+ if ($this->definition() === null) {
+ $this->ensureWellFormed(false);
+ // The expression is guaranteed to have 0 or 1 arguments because it's well formed.
+ if (count($this->args()) == 0) {
+ return '';
+ }
+ if ($this->args()[0] instanceof ElementInstance) {
+ return $this->args()[0]->getRepresentation();
+ } else {
+ return $this->args()[0]->match();
+ }
+ } else {
+ return $this->definition()->getRepresentation($this);
+ }
+ } finally {
+ --$stack_depth;
+ }
+ }
+
  public function isExpanded($recursive=true) {
  static $stack_depth = 0; global $STACK_LIMIT;
  if (++$stack_depth > $STACK_LIMIT) {
@@ -518,6 +543,47 @@ class ElementDefinition {
  return $this->_evaluateWellFormed($elmInstance);
  }
 
+ public function getTokenDefRepr($idx) {
+ if ($idx < count($this->tokenDefs())) {
+ return $this->tokenDefs()[$idx]->representation();
+ } elseif (count($this->tokenDefs()) == 1) {
+ return $this->tokenDefs()[0]->representation();
+ }
+ return '';
+ }
+
+ public function getRepresentation($elmInstance) {
+ $this->ensureWellFormed($elmInstance);
+ $argsRepr = array();
+ foreach ($elmInstance->args() as $arg) {
+ if ($arg instanceof TokenInstance) {
+ $argsRepr[] = $arg->match();
+ } else {
+ $argsRepr[] = $arg->getRepresentation();
+ }
+ }
+ $pieces = array();
+ if ($this->fixing() == Fixing::Prefix || $this->fixing() == Fixing::Wrap) {
+ $pieces[] = $this->getTokenDefRepr(0);
+ }
+ $argIdx = ($this->fixing() == Fixing::Postfix || $this->fixing() == Fixing::Infix ? -1 : 0);
+ foreach ($argsRepr as $argRepr) {
+ $pieces[] = $argRepr;
+ ++$argIdx;
+ if ($this->fixing() == Fixing::None && $this->fixing() == Fixing::Wrap) {
+ continue;
+ }
+ if ($argIdx >= count($argsRepr) || ($this->fixing() == Fixing::Infix && $argIdx >= count($argsRepr) - 1)) {
+ continue;
+ }
+ $pieces[] = $this->getTokenDefRepr($argIdx);
+ }
+ if ($this->fixing() == Fixing::Wrap) {
+ $pieces[] = $this->getTokenDefRepr(1);
+ }
+ return implode('', $pieces);
+ }
+
  static public function extractUsedTokens($elmDefs) {
  $retval = array();
  foreach ($elmDefs as $elmDef) {

test.php

@@ -5,7 +5,10 @@ require_once "grammar.php";
 $text = 'usr1 ||(!usr2&&@group || !usr3)';
 echo 'Parsing "' . $text . '".' . "\n";
 $expr = parse($text);
+echo "Tree representation:\n";
 $expr->printTree();
+echo "Value:\n";
 var_dump($expr->evaluate());
-
+echo "Reconstructed expression:\n";
+echo $expr->getRepresentation() . "\n";
 ?>
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