From: ES <ruby-ml@...>
Date: 2005-10-13T04:28:45+09:00
Subject: Re: Default argument values for blocks

Christophe Grandsire wrote:
> Selon Thomas <sanobast-2005a@yahoo.de>:
> 
> 
>>I was dreaming for a long time of a ruby dialect that has all these
>>fancy arrows haskell has. Everybody proposing arrows, please (try to)
>>read some haskell code.
>>
> 
> 
> I have and can only concur. The arrows make things pretty confusing in most
> places.
> 
> 
>>But seriosly, I personally would prefer something in the line lambda(x,
>>y=1) {...} as it was proposed by other people too.
>>
> 
> 
> The problem is that "collection.each lambda(foo="bar") {puts foo}" has to be the
> ugliest and most long-winded thing I've seen in a long time. It's OK for making
> a Proc, but to use as a block it's just plain wrong.

So do not use it as a block. This syntax only solves the default args (etc.)
problem but does not in any way invalidate the block syntax (which, as Matz
has pointed out many times, is not going anywhere).

   collection.each {|foo| puts foo}

and

   block = lambda(foo = 'bar') { puts foo }

> However, it's nearly impossible a problem to solve. Any solution will probably
> look rather awful. We just need to find the least offensive one :) . Unless one
> finds a way to parse "{|foo="bar"| puts foo}" correctly. That'd be the best
> solution.
> 
> 
>>The => in the hash syntax is IMHO already one kind of arrow too much.
>>
> 
> 
> Hasn't a change been accepted that allows one to use ":" as an alternative to
> "=>" in hashes?
> 
> Hey, what about ":(foo="bar"){puts foo}"? It's still not beautiful but it's
> still less annoying, and in Ruby we are already used to see colons at the
> beginning of a word. Of course, overloading ":" may not be considered a good
> idea, but it shouldn't be a parsing problem as this one would always be
> followed by a "(" (and that doesn't happen with symbols). And:
> 
> collection.each:(foo="bar"){puts foo}
> 
> isn't that bad :) .
> --
> Christophe Grandsire.

E