Re: Type hinting - Request for Discussion

troels knak-nielsen wrote:

1) It covers all the use cases for a type-based system (You can use is_integer as a contract, if you want that) 2) It's extensible in user-space, which means that it can be used to convey much more accurate information, relevant to the application needs. 3) It's focused on the interface of input-parameters, rather than their type.

This is my favorite alternative so far. There are just a few problems with parsing as I see it. - How do you know if it is a contract or the current object type hint? - It doesn't allow a type to be forced (casted) to the correct type. To address these items, I suggest the following changes. Change the syntax of the contract to look like a function call (which is essentially what we are doing): <?php function array_of_numeric($x) {

      if (!is_array($x)) {
          return false;
      }
      foreach ($x as $val) {
          if (!is_numeric($val)) {
              return false;
          }
      }
      return true;

} function sum(array_of_numeric($a)) {

      return array_sum($a);

} This could even be extended to allow for more generic types by allowing constant parameters for the contract: <?php function array_of($x, $type) {

      if (!is_array($x)) {
          return false;
      }
      switch ($type) {
          case 'int':
              $check = 'is_int';
              break;
          case 'float':
              $check = 'is_float';
              break;
          case 'numeric':
              $check = 'is_numeric';
              break;
          case 'string':
              $check = 'is_string';
              break;
          case 'bool':
              $check = 'is_bool';
              break;
          default:
              return false;
      }
      foreach ($x as $val) {
          if (!$check($val)) {
              return false;
          }
      }
      return true;

} function sum(array_of($a, 'numeric')) {

      return array_sum($a);

} To allow for casting, the contract function could take the value by reference and cast it: <?php function array_of_float(&$x) {

      if (!is_array($x)) {
          return false;
      }
      foreach ($x as $key => $val) {
          if (!is_numeric($val)) {
              return false;
          }
          $x[$key] = (float)$val;
      }
      return true;

} function sum(array_of_float($a)) {

      return array_sum($a);

} -- Joshua Thompson Mechanical Engineer/Software Developer http://www.schmalls.com