Prototype

Comments and changes to this ticket

• 

  Juriy Zaytsev April 26th, 2008 @ 05:50 PM

  • → State changed from “new” to “enhancement”
• 

  John-David Dalton April 26th, 2008 @ 09:07 PM

  what about being more granular and having a String#toFunction()

• 

  Juriy Zaytsev April 26th, 2008 @ 09:59 PM

  Because I don't see other use cases besides using string as an iterator. toFunction is pretty easy to implement and do you really think it's worth adding another String.prototype method (if toIterator is enough) ? : )

  String.prototype.toFunction = function(){
    return new Function(arguments[0], this);
  }
  
  ' return x + y '.toFunction('x, y');
  
  // creates
  function (x,y) {
    return x + y;
  }
  

• 

  Josh Strater April 30th, 2008 @ 10:12 PM

  Oliver Steele's Functional Javascript library offers automatic conversion of strings to functions, and not just for iterators. For arguments, one can either use Haskell-style parameter lists or implicit parameters. The syntax also allows for more of a pointfree style. For example:

  map('1+', [1,2,3]) → [2, 3, 4]
  

  It's actually pretty clever.

  Anyway, if this is the kind of feature that Prototype wants to include, Steele's library would seem to be a good starting point.

• 

  Juriy Zaytsev May 1st, 2008 @ 05:22 AM

  Josh,

  I'm a big fan of Oliver's "Functional".

  The idea, though, was to provide support for a minimal "sugar" - to keep backwards compatibility and not to cripple performance much.

  If we drop explicit "return" from the iterator-string, the syntax becomes quite concise (too concise?):

  [1,2,3].map('value + 1'); // => [2,3,4]
  
  $R(1,10).findAll('value < 5'); // => [1,2,3,4]
  

  The reason I made "return" explicit is to have support for multiple expressions:

  [1,2,3].map(' console.log(index, value); return value + 1; ');
  

  Dropping "value" would lead to some heavy parsing, and I'm worried about performance issues (though we would certainly need benchmarks for that).

  Feel free to submit patch/tests if you like.

  Best,

  kangax

• 

  Juriy Zaytsev May 1st, 2008 @ 05:32 AM

  Now that I think about it, "return" could be prepended only if it's not present in expression. That would be fast and concise:

  [1,2,3].map(' value + 1 '); // return is not present, prepend it
  [1,2,3].map(' console.log(index); return value + 1 '); // return is present, do nothing
  

• 

  matthuhiggins May 1st, 2008 @ 06:22 AM

  For sortBy, max, min and perhaps some others, I would more commonly just want to pass in a property name or method to invoke.

  var friends = [{name: 'joe', age: 10}, {name: 'bob', age: 12}];
  
  var oldest = friends.max('age');
  var alphaSorted = friends.sortBy('name');
  

  The reason I bring this up is because you cannot easily support the suggested change in this ticket and the property name approach at the same time.

• 

  John-David Dalton May 1st, 2008 @ 07:46 PM

  @matthuhiggins - Your suggestion leaves a lot of guessing on Prototype's part.

  I think if you follow Juriy's syntax you can accomplish the same thing.

  var friends = [{name: 'joe', age: 10}, {name: 'bob', age: 12}];
  
  var oldest = friends.max('value.age');
  var alphaSorted = friends.sortBy('value.name');