Added two function methods _.curry and _.attach (+ tests)

[alexindigo]

• _.curry – Curries (burns in) arguments to a function, without forcing new context (inspired by prototypejs).

Difference between _.curry and _.bind: http://jsfiddle.net/CqG7n/

• _.attach – Attaches new properties to the context of the call, in other words it extends passed object(s) with 'this' and makes it context.

To illustrate my use case I modified example from flatiron/director

// api.js
  function helloWorld(route) {
    this.res.writeHead(200, { 'Content-Type': 'text/plain' })
    this.res.end('hello world from (' + route + ')');
  }

// router.js
  var router = new director.http.Router({
    '/hello': {
      get: helloWorld
    }
  });

And I want to provided to my handlers stuff like db-resourse, application home path, etc.,
without expanding list of function parameters, but rather adding to the context.

Using _.attach

// api.js
  function helloWorld(route) {
    fs.readFile(this.apphome+'/etc/passwd', function (err, data) {
      this.res.writeHead(200, { 'Content-Type': 'text/plain' })
      this.res.end(data);
    });
  }

// router.js
  var apphome = '/var/www';
  var router = new director.http.Router({
    '/hello': {
      get: _.attach(helloWorld, {apphome: apphome})
    }
  });

[alexindigo]

@lvivski Partial is specific to the language implementation, like Haskel, where you can pass partial number of parameters and in return get function for remaining parameters. I think it could be implemented in javascript. But I don't see practical value for that. And on javascript side curry is well-known in the community in this particular implementation because of PrototypeJS. I believe it would be less confusing to have it this way rather than trying to make Haskel out of javascript.

[liamks]

Great idea! Curry is an important part of functional programming.

[prust]

FWIW, I agree that it would be nice to have _.curry. Our team migrated from prototypejs to underscore and this is one of the holes in underscore. I find myself using fn.bind(null, arg1) instead, which isn't as readable/explicit.

[alexindigo]

Curry is handy for many different ways, and fn.bind(null, arg1) is not 100% replacement, as I showed here: http://jsfiddle.net/CqG7n/

[alexindigo]

And recently I bumped into another library that might replace underscore for some scenarios, it has many goodies including curry: https://github.com/ded/valentine

[jashkenas]

Let's move this conversation over into #474...