From: "Ondřej Bílka" <neleai@...>
Date: 2012-03-17T21:07:06+09:00
Subject: [ruby-core:43367] Arguments, assignment and pattern matching.

Hello,

I wonder what should be ideal way to pass arguments and do mass assignment. 

First a question: What should following code do in ruby2.0?
def foo(x,*y,z)
  puts [x,y,z]
end
foo(1,2,y:[1,2])

I assume that arguments can be captured in Argument object. This gives
us also multiple return for free.
def foo(*a);a;end
foo(1,2,x:1,y:2) # Argument[1,2]{x:1,y:2}
[3,4,a:1,b:2]    # Argument[3,4]{a:1,b:2}

Argument object extends array and you can access named arguments via
arguments method.

I plan extend ruby with pattern matching in my amethyst project. My
current vision is following:

[a,[b,c]]= [1,[2,3]]

amethyst Amethyst {
  tree = Tree #Class pattern matches objects of given class
       | Leaf -> Tree[nil,nil]
}
def foo( _:(Int:x | Float:y) , _:tree[ l:@left,r:@right ])
  return [4,l,a:x,b:y]
end

[ z,l, a:@a, b:@b ]= foo(1,Tree[1,2])
[ z,l, a:@a, b:@b ]= foo(1,Leaf[])

This could be way how add more flexible splat when I am done.

How it is similar to current plan of keyword arguments?

-- 

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