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<?phpnamespace eMacros\Runtime\Symbol;
 
 use eMacros\Applicable;
 use eMacros\Scope;
 use eMacros\GenericList;
 
 class SymbolLookup implements Applicable {
 /**
 * Obtains a symbol value from current environment
 * Usage: (lookup "_value")
 * Returns: mixed
 * (non-PHPdoc)
 * @see \eMacros\Applicable::apply()
 */
 public function apply(Scope $scope, GenericList $arguments) {
 if (count($arguments) == 0) {
 throw new \BadFunctionCallException("SymbolLookup: No parameters found.");
 }
 
 $ref = $arguments[0]->evaluate($scope);
 
 if (!is_string($ref) || empty($ref)) {
 throw new \InvalidArgumentException("SymbolLookup: Symbol must be specified as a non-empty string.");
 }
 
 if (!array_key_exists($ref, $scope->symbols)) {
 throw new \InvalidArgumentException(sprintf("SymbolLookup: Symbol %s does not exists on current environment.", $ref));
 }
 
 return $scope->symbols[$ref];
 }
 }
 ?>
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