On Sun, Aug 23, 2009 at 4:53 PM, David A. Black <dblack / rubypal.com> wrote:

> Hi --
>
> On Mon, 24 Aug 2009, Yehuda Katz wrote:
>
>>
>> The compelling this for me is that it makes methods that take multiple
>> blocks easier for programmer to read. For programmer, one big confusion in
>> Ruby is difference between proc, block, lambda and method. Unifying syntax
>> for block and proc shows that they are really just same thing, with proc
>> passed as parameter and block passed as special parameter.
>>
>
> I have to admit that this strikes me as a solution in search of a
> problem, in that I've never had any trouble reading methods that take
> Proc objects as arguments. Also, I think that with the unification of
> block and method parameter semantics, things are getting a lot less
> confusing as to the differences among them.


I can just speak for myself: the fact that there were multiple different
"code block" syntaxes, each with their own semantics, has been a source of
historical pain for me.


> I don't consider a block to be the same thing as a proc, nor do I
> consider it a method argument. The block is part of the method-call
> syntax; in itself, it isn't an object (just as the argument list is
> not, in itself, an object).


There's no conceptual reason for programmers to differentiate between Proc
objects and the block passed to methods, except that the latter provides
some extra syntax to make the common use-case pretty. Trying to explain the
difference to new Rubyists strikes me as something we'd be better off never
having to do.


>  Then whenever programmer sees { something } they know it is "proc" with
>> lexical scope, and whenever programmer sees ->{ something } they know it
>> is
>> "lambda" with function scope.
>>
>
> One danger of { something } being a proc is that it does away with the
> error message for odd-numbered hashes -- an edge case, admittedly, but
> still.


I don't think I've ever encountered this error except for Hash[*something],
which would not be affected by this change.


>  I would even be in favor of def { } as lambda syntax, which would make
>> clear
>> to programmer that this block behaves just like normal method. Then we
>> have
>> just two things: def for method-scope (def something() end and def { })
>> and
>> bare { } for block scope.
>>
>
> Dave Thomas brought up the def { } thing at RubyConf 2005, I believe,
> and got a big round of applause :-) It's definitely way better than
> ->() (which I still sort of hope will disappear, though my hope is
> fading).


Then we agree :)

Don't you think that having just two "keywords" for code blocks (def/bare
{}) would simplify things conceptually?


>
>
>
> David
>
> --
> David A. Black / Ruby Power and Light, LLC / http://www.rubypal.com
> Q: What's the best way to get a really solid knowledge of Ruby?
> A: Come to our Ruby training in Edison, New Jersey, September 14-17!
>   Instructors: David A. Black and Erik Kastner
>   More info and registration: http://rubyurl.com/vmzN
>
>


-- 
Yehuda Katz
Developer | Engine Yard
(ph) 718.877.1325