From: "David A. Black" <dblack@...>
Date: 2004-12-01T20:16:56+09:00
Subject: Re: Optional static typing (or, What can Ruby 2.0 borrow from Boo?)

Hi --

On Wed, 1 Dec 2004, Lothar Scholz wrote:

> Hello gabriele,
> 
> gr> Lothar Scholz ha scritto:
> 
> 
> gr> Anyway, notice that I submitted  RCR280 wich actually allow you to give
> gr> type assertions if you want them:
> 
> I must say that i don't like it because it mixes again runtime and
> compile time. i would really favour:
> 
> # if you want to add an integer to a subclass of Numeric
>  def sum a,b
>    assert_type "a => Numeric, b = Integer"
>    a+b
>  end
> 
> Only if everything can be extracted statically (by looking at the code)
>  then you get into a better position then what is currently available.
>  
>  Mixing another special feature like conversion into this is something
>  i absolutely don't like. Two different purposes should have to
>  different notations. Also your RCR makes the situation worse, adding
>  more invisble magic. But the main goal here is to be more verbose.
> 
>  The assert_type could be extended to help with collections and other
>  things a little bit:
> 
>  assert_type "h => Hash[Integer], object.foo = String, @myvar = Dummy"

If you're going to write this, or propose it as an RCR, it would be
better to call it "assert_class", or "assert_isa", to keep clear the
important distinction between type and class in Ruby and the fact that
this is a class-name/hierarchy check, rather than a type check.


David

-- 
David A. Black
dblack@wobblini.net