code: public function apply(Scope $scope, GenericList $arguments) {
  		$nargs = count($arguments);
  		if ($nargs < 3) throw new \BadFunctionCallException("StringReplace: Function expects at least 3 parameters.");
  		if ($nargs == 3) return call_user_func($this->callback, $arguments[0]->evaluate($scope), $arguments[1]->evaluate($scope), $arguments[2]->evaluate($scope));
  		else {
  			$target = $arguments[3];
  			if (!($target instanceof Symbol))
  				throw new \InvalidArgumentException(sprintf("StringReplace: Expected symbol as fourth argument but %s was found instead.", substr(strtolower(strstr(get_class($arguments[3]), '\\')), 1)));
  			$func = $this->callback;
  			return $func($arguments[0]->evaluate($scope), $arguments[1]->evaluate($scope), $arguments[2]->evaluate($scope), $scope->symbols[$target->symbol]);
  		}
  	}
docs: Replace ocurrences of a tring in another
  Usage: (String::replace _str1 _str2 _subject) (String::ireplace _str1 _str2 _subject)
  Returns: string
  (non-PHPdoc)
  @see \eMacros\Applicable::apply()