From: Brian Candler <B.Candler@...>
Date: 2007-05-31T21:49:49+09:00
Subject: Re: Introducing the "it" keyword

On Thu, May 31, 2007 at 09:32:28PM +0900, Jacob Burkhart wrote:
> consider the clarity of reading these:
> 
> with(v+1) do |a|
>    with(x+2) do |b|
>        return a if a+b < 10
>    end
> end
> 
> vs.
> 
> with:a(v+1) do
>    with:b(x+2) do
>        return a if a+b < 10
>    end
> end

How about also comparing it with:

(1)

with(v+1, x+2) { |a, b|
  return a if a+b < 10
}

(2)

a = v+1                  # or: a, b = v+1, x+2
b = x+2                  #
return a if a+b < 10

(3)

local {
  a = v+1                # or: a, b = v+1, x+2
  b = x+2                #
  return a if a+b < 10
}

All these can be implemented without any language changes.

Now, if you could assign default parameters in blocks, you'd have another
option:

(4)

let { |a=v+1, b=x+2|
  return a if a+b < 10
}

Having default values for block arguments would be a boon for other reasons,
including being able to rationalise some of the differences between the
various flavours of blocks, procs and methods.

The main difficultly seems to be the ambiguity of '|' as an operator or the
end of a parameter list.

Regards,

Brian.