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Comment by nnq | Hacker News Reader

> but I tend to write very functional code

A bit offtopic, but since you said that and you seem to be both fond of functional programming and in touch with latest ruby developments, you're probably a good person to ask: How the heck do you do "normal/proper" currying in Ruby? And how do you do it with keyword arguments? (I'm trying to compile a list of functional-idiom examples in popular dynamic language, and when I reached Ruby and currying, all the snippets I found made me go "WTF?!"...)

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Ruby only has built-in support for currying procs:

  >> add = -> x, y { x + y }
  => #<Proc (lambda)>
  >> add.call(3, 5)
  => 8
  >> add.call(3)
  ArgumentError: wrong number of arguments (1 for 2)
  >> curried_add = add.curry
  => #<Proc (lambda)>
  >> add_three = curried_add.call(3)
  => #<Proc (lambda)>
  >> add_three.call(5)
  => 8

If you want a no-brainer way of currying methods, you're SOL.

That's pretty much it; the only other way is to build a function combinator from a Proc or Lambda:

irb(main):004:0> multiply = -> a, b { a * b } => #<Proc:0x007fe2822029e0@(irb):4 (lambda)>

irb(main):006:0> square = -> a { multiply.call(a, a) } => #<Proc:0x007fe2840746a8@(irb):6 (lambda)>

irb(main):007:0> square.call(3) => 9

You can do:

    "Hello".method(:split).to_proc.curry[""]
     => ['H', 'e', 'l', 'l', 'o']

If you want to even make the receiver an argument it would take a little more hoop jumping, but with a tiny monkey patch you can enable something like this:

    "Hello".curry.split[""]

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