Asp Forum - syntax sugar: treating an object like a method

Eric Mahurin

5/18/2005 5:00:00 PM

I'm thinking of yet another RCR and would like to see if
anybody likes it. I think this would be a sweet feature. Here
are the basic components:

1. Allow a null/default method to be defined in a class so that
the syntax "obj(*args,&block)" could be used. obj could be any
expression yielding a object. When you try to treat that
object as a method passing arguments and/or attaching a code
block to it, the null/default method would be called. I was
thinking "@" would be a good name for this method - like "+@"
and "-@". Here are a few example uses:

* klass(*args) : you alias the null method to "new" so that
this would be equivalent ot klass.new(*args). I tend to forget
the ".new" more often than I'd like to admit.

* obj() : this could be aliased to clone in Object so that
default would be to just obj.clone

* enum {...} : you could alias the null method to "each" so
that this would be equivalent to enum.each {...}

2. Allow an assignment method to be defined for an object ('='
is probably best). This would be called when you find an
object expression on the LHS whereas #1 is the equivalent for
the RHS. The ugly thing about this is that you have to make
sure that the object being assigned looks like an expression as
opposed to a variable or attribute assignment - surrounding is
parentheses makes it an expression that is normally illegal to
assign to. Along with '=', '+=', '-=', etc. becomes meaningful
in this context. You could also incorporate RCR 157/307 in
there allowing arguments. Here are a few example uses for
this:

* (str) = value : this could default to "replace" for any
objects that respond to it (or if you use evil.rb - "become")

* (mutable) += value : now the real += can be implemented for
this since you are accessing the object rather than assigning
the variable. Of course Fixnum is immutable, so it doesn't do
you any good there. Other mutable classes (or ones that could
be made mutable - Float) could take advantage of this (for
example Array).

I was mainly wanting #1, the complementary #2 looks pretty
useful too.

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8 Answers

Brian Schröder

5/18/2005 5:19:00 PM

On 18/05/05, Eric Mahurin <eric_mahurin@yahoo.com> wrote:
> [snip]
> * klass(*args) : you alias the null method to "new" so that
> this would be equivalent ot klass.new(*args). I tend to forget
> the ".new" more often than I'd like to admit.
> [snip]

I don't know if I like this proposal, but in any case I'd expect a syntax like:

class A
def initialize(x)
@x = x
end

def self.[](x)
self.new(x)
end

def self.()(x)
self.new(x)
end
end

A[12]
A(12)

for it. (Note that the square brackets already work.)

best regards,

Brian

--
http://ruby.brian-sch...

Stringed instrument chords: http://chordlist.brian-sch...

dblack

5/18/2005 6:00:00 PM

Austin Ziegler

5/18/2005 6:31:00 PM

On 5/18/05, Eric Mahurin <eric_mahurin@yahoo.com> wrote:
> I'm thinking of yet another RCR and would like to see if
> anybody likes it. I think this would be a sweet feature. Here
> are the basic components:

Please don't. This would be awful. Ruby doesn't need a () operator.

-austin
--
Austin Ziegler * halostatue@gmail.com
* Alternate: austin@halostatue.ca

ES

5/18/2005 7:08:00 PM

Le 18/5/2005, "Austin Ziegler" <halostatue@gmail.com> a écrit:
>On 5/18/05, Eric Mahurin <eric_mahurin@yahoo.com> wrote:
>> I'm thinking of yet another RCR and would like to see if
>> anybody likes it. I think this would be a sweet feature. Here
>> are the basic components:
>
>Please don't. This would be awful. Ruby doesn't need a () operator.

Oh, never say never. I still fantasize about first-order functions/
methods (although that need would probably be better served by other
means). For this particular purpose I would tend to agree, though.

>-austin

E

--
template<typename duck>
void quack(duck& d) { d.quack(); }

Austin Ziegler

5/18/2005 8:52:00 PM

On 5/18/05, ES <ruby-ml@magical-cat.org> wrote:
> Le 18/5/2005, "Austin Ziegler" <halostatue@gmail.com> a écrit:
>> On 5/18/05, Eric Mahurin <eric_mahurin@yahoo.com> wrote:
>>> I'm thinking of yet another RCR and would like to see if anybody
>>> likes it. I think this would be a sweet feature. Here are the
>>> basic components:
>> Please don't. This would be awful. Ruby doesn't need a ()
>> operator.
> Oh, never say never. I still fantasize about first-order
> functions/ methods (although that need would probably be better
> served by other means). For this particular purpose I would tend
> to agree, though.

As I understand it, Ruby already has first-order functions; they're
just not (currently) callable with foo(). Ruby 1.9 has an
experimental change that does this for local variables that have
Methods or Procs in them.

At the very least, no one has been able to explain to me why what
Ruby does isn't acceptable. I don't want or need Ruby to be Python
and I don't want or need a () operator.

-austin
--
Austin Ziegler * halostatue@gmail.com
* Alternate: austin@halostatue.ca

gabriele renzi

5/18/2005 9:01:00 PM

Austin Ziegler ha scritto:

>>Oh, never say never. I still fantasize about first-order
>>functions/ methods (although that need would probably be better
>>served by other means). For this particular purpose I would tend
>>to agree, though.
>
>
> As I understand it, Ruby already has first-order functions; they're
> just not (currently) callable with foo(). Ruby 1.9 has an
> experimental change that does this for local variables that have
> Methods or Procs in them.

AFAIK it does work (reasonably to me) for everything that has #call.

> At the very least, no one has been able to explain to me why what
> Ruby does isn't acceptable. I don't want or need Ruby to be Python
> and I don't want or need a () operator.
>

it *is* acceptable, *I* would just prefer some syntax sugar.
I mean,
x.foo()
is quite acceptable but I think
x.foo
is nicer.

Paul Brannan

5/19/2005 2:14:00 PM

On Thu, May 19, 2005 at 02:00:04AM +0900, Eric Mahurin wrote:
> I'm thinking of yet another RCR and would like to see if
> anybody likes it. I think this would be a sweet feature. Here
> are the basic components:

These really sound like two separate change requests to me.

> 1. Allow a null/default method to be defined in a class so that
> the syntax "obj(*args,&block)" could be used. obj could be any
> expression yielding a object. When you try to treat that
> object as a method passing arguments and/or attaching a code
> block to it, the null/default method would be called. I was
> thinking "@" would be a good name for this method - like "+@"
> and "-@". Here are a few example uses:
>
> * klass(*args) : you alias the null method to "new" so that
> this would be equivalent ot klass.new(*args). I tend to forget
> the ".new" more often than I'd like to admit.
>
> * obj() : this could be aliased to clone in Object so that
> default would be to just obj.clone
>
> * enum {...} : you could alias the null method to "each" so
> that this would be equivalent to enum.each {...}

What you propose requires a change in name lookup rules. I suggest you
consider what the current rules are and what you would like them to be
before you submit an RCR.

Also, consider that Ruby already has a mechanism for callable objects;
any object that is callable responds to the call() method (consider
Proc and Method).

Paul

ES

5/19/2005 4:24:00 PM

Austin Ziegler wrote:
> On 5/18/05, ES <ruby-ml@magical-cat.org> wrote:
>
>>Le 18/5/2005, "Austin Ziegler" <halostatue@gmail.com> a écrit:
>>
>>>On 5/18/05, Eric Mahurin <eric_mahurin@yahoo.com> wrote:
>>>
>>>>I'm thinking of yet another RCR and would like to see if anybody
>>>>likes it. I think this would be a sweet feature. Here are the
>>>>basic components:
>>>
>>>Please don't. This would be awful. Ruby doesn't need a ()
>>>operator.
>>
>>Oh, never say never. I still fantasize about first-order
>>functions/ methods (although that need would probably be better
>>served by other means). For this particular purpose I would tend
>>to agree, though.
>
>
> As I understand it, Ruby already has first-order functions; they're
> just not (currently) callable with foo(). Ruby 1.9 has an
> experimental change that does this for local variables that have
> Methods or Procs in them.

First-order method meaning here that methods are just a special
case of a block that has been bound to a particular object. They
would be fully rebindable, copyable and assignable. Essentially,
in a way, simply method dicts.

> At the very least, no one has been able to explain to me why what
> Ruby does isn't acceptable. I don't want or need Ruby to be Python
> and I don't want or need a () operator.

What Ruby does is perfectly fine. True first-order would yield some
more flexibility.

> -austin

E

--
template<typename duck>
void quack(duck& d) { d.quack(); }

comp.lang.ruby

syntax sugar: treating an object like a method

Eric Mahurin

Brian Schröder

dblack

Austin Ziegler

ES

Austin Ziegler

gabriele renzi

Paul Brannan

ES

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