Partial Application

[alexispurslane]

I think that currying would be highly convenient in a stream-based programming language! Check this out:

seq(100) | (% 5) | STDOUT

or

seq(100) | (_ % 5) | STDOUT

[alexispurslane]

So that when you call a function with missing arguments, it returns another function that takes the rest of those arguments. That would be great for streem because then we can use functions lake transformations and filters, passing in one argument, and letting the stream fill in the rest! Otherwise, we would have to do this:

seq(100) | {|x| 
  if x % 5 {
    x
  }
} | STDOUT

[nickserv]

That seems pretty awesome, I agree that currying would be pretty useful in this situation.

However, how would this affect calling syntax? For example, what if there are optional parameters? Also, if there is not a lot of type checking going on, this could confuse people if they curry by accident.

[alexispurslane]

I was thinking using an underscore for a missing parameter. That way function calls, optionals, and so-on wouldn't be confused:

seq(100) | (_ % 5) | STDOUT

[pvwoods]

depending on data type support within the language, how would tuple/set access work?

(_._1 % 5) or (_[0] % 5) come to mind... not sure what would be the cleanest option.

[shouya]

+1 for the currying. Also take a look at this pretty awesome gem https://cirw.in/blog/ampex, which enables you to do more complex shorthand operations like &X ** 2 / 2 instead of -> {|x| x ** 2 / 2}.

[shouya]

@ChristopherDumas That's kinda like what you can do in Scala's anonymous functions... I don't know what is this syntax's name.

[nickserv]

Would _ be used for a curried parameter or an optional parameter?

[alexispurslane]

_ would be a curried parameter. Optional parameters just wouldn't be supplied, just missing. (......of course, we could do it the other way around........)

[shuichiro-makigaki]

Currying is good idea, and I'd like to add +1. But, if Streem supports bit operation, I'm afraid:

seq(100) | (_ | 3 | 5) | STDOUT

hmm, too many bars... The proposed syntax looks good to me, but users shouldn't use complex operations in currying!

[alexispurslane]

Agreed, but that is more of a stylistic issue.

[dajoh]

Shouldn't (_ % 5) or (% 5) be a function from Int -> Int, and not Int -> Maybe Int as this implies:

{|x| 
  if x % 5 {
    x
  }
}

That function also doesn't have the same "output integer" (x vs x mod 5).

[dajoh]

Also, this isn't called currying, this is called partial application. I suggest you change your wording.

[alexispurslane]

Got it. Changing issue name....