Asp Forum - proposal for a named parameter prefix

quixoticsycophant

9/6/2003 7:08:00 PM

def foo(*array)
array.each do |a|
# ...
end
end

Aha there's an asterisk so we know it's an array.

def foo2(&block)
@callback = block
# ..
end

Aha there's an ampersand so we know it's a block.

def foo3(what_is_this)
# ...
# (many lines of code)
# ...
what_is_this.each |key,value|
# ...
end
end

Hm what is what_is_this? <scroll scroll scroll> Aha I see it's the
ol' named-parameter thing.

But wait there's more! I can't do

foo4(some, variable, number, of, elements,
:then => some, :named => parameters)

because such a definition

foo4(*array, params)
# ...
end

would be illegal since params would be splatted into the array.

I propose:

def foo4(*array,%params,&block)
array.each do |a|
# ...
end
params.each do |key, value|
# ...
end
@callback = block
end

from above,

def foo3(%what_is_this)
# ...
end

Aha there's a percent sign so we know it's a hash.

It'll be backward compatible too. You'll just get the current
behavior when there's no percent sign. Also, the hash in

foo4( { :a => 4, :b => 5, :c => 6 } )

will be treated as a normal array argument.

To summerize, "%" gets us two things

(1) a nice signal to let everyone know a named parameter hash is
there

(2) the ability to mix variable-length arguments with named
parameters (in a nice way)

--
Jeff Mitchell

8 Answers

nobu.nokada

9/7/2003 10:06:00 AM

Hi,

At Sun, 7 Sep 2003 04:13:18 +0900,
Jeff Mitchell wrote:
> I propose:
>
> def foo4(*array,%params,&block)
> array.each do |a|
> # ...
> end
> params.each do |key, value|
> # ...
> end
> @callback = block
> end
>
> from above,
>
> def foo3(%what_is_this)
> # ...
> end
>
> Aha there''s a percent sign so we know it''s a hash.

Why does a percent sign mean a hash?

> To summerize, "%" gets us two things
>
> (1) a nice signal to let everyone know a named parameter hash is
> there
>
> (2) the ability to mix variable-length arguments with named
> parameters (in a nice way)

IIRC, matz has thought ** for it.

--
Nobu Nakada

quixoticsycophant

9/7/2003 4:24:00 PM

nobu.nokada@softhome.net wrote in message news:<200309071005.h87A5o4D004546@sharui.nakada.kanuma.tochigi.jp>...
> Hi,
>
> At Sun, 7 Sep 2003 04:13:18 +0900,
> Jeff Mitchell wrote:
> > I propose:
> >
> > def foo4(*array,%params,&block)
> > array.each do |a|
> > # ...
> > end
> > params.each do |key, value|
> > # ...
> > end
> > @callback = block
> > end
> >
> > from above,
> >
> > def foo3(%what_is_this)
> > # ...
> > end
> >
> > Aha there''s a percent sign so we know it''s a hash.
>
> Why does a percent sign mean a hash?

Because it was the arbitrary character I chose in the proposal above.

Also, "coincidentally", it happens to be perl''s sigil for hash (just like
"&" happens to be perl''s sigil for code block).

It doesn''t have to be a hash per se, just "the thing that holds named
parameters".

>
> > To summerize, "%" gets us two things
> >
> > (1) a nice signal to let everyone know a named parameter hash is
> > there
> >
> > (2) the ability to mix variable-length arguments with named
> > parameters (in a nice way)
>
> IIRC, matz has thought ** for it.

Hm? My first reaction is that it would be confusing since ** suggests
"splat twice" (whatever that means).
--
Jeff

quixoticsycophant

9/7/2003 5:13:00 PM

nobu.nokada@softhome.net wrote in message news:<200309071005.h87A5o4D004546@sharui.nakada.kanuma.tochigi.jp>...
>
> > To summerize, "%" gets us two things
> >
> > (1) a nice signal to let everyone know a named parameter hash is
> > there
> >
> > (2) the ability to mix variable-length arguments with named
> > parameters (in a nice way)
>
> IIRC, matz has thought ** for it.

Can you give a link to this discussion? I haven''t been able to find
it on google, rubygarden, etc.

thanks
--
Jeff

Sean O'Dell

9/7/2003 9:49:00 PM

Jeff Mitchell wrote:
> nobu.nokada@softhome.net wrote in message news:<200309071005.h87A5o4D004546@sharui.nakada.kanuma.tochigi.jp>...
>
>>>To summerize, "%" gets us two things
>>>
>>> (1) a nice signal to let everyone know a named parameter hash is
>>> there
>>>
>>> (2) the ability to mix variable-length arguments with named
>>> parameters (in a nice way)
>>
>>IIRC, matz has thought ** for it.
>
>
> Can you give a link to this discussion? I haven''t been able to find
> it on google, rubygarden, etc.

If it''s possible, I would prefer that Ruby DOESN''T get another
#$%^-style idiosyncracy added. Why can''t named parameters just go
something like this:

def method(param1)
end

method(:param1 = "value")

....and just accept parameters as normal, except when the first named
parameter is encountered, assume the remaining parameters sent from a
call are out-of-order and will also be named parameters. In other
words, handle it transparently to the method, backwards-compatible with
existing code and without a new non-letter-character being used to
denote a syntax idiom.

Sean O''Dell

Hal E. Fulton

9/7/2003 10:49:00 PM

Sean O''Dell wrote:
> Jeff Mitchell wrote:
>
>> nobu.nokada@softhome.net wrote in message
>> news:<200309071005.h87A5o4D004546@sharui.nakada.kanuma.tochigi.jp>...
>>
>>>> To summerize, "%" gets us two things
>>>>
>>>> (1) a nice signal to let everyone know a named parameter hash is
>>>> there
>>>>
>>>> (2) the ability to mix variable-length arguments with named
>>>> parameters (in a nice way)
>>>
>>>
>>> IIRC, matz has thought ** for it.
>>
>>
>>
>> Can you give a link to this discussion? I haven''t been able to find
>> it on google, rubygarden, etc.
>
>
> If it''s possible, I would prefer that Ruby DOESN''T get another
> #$%^-style idiosyncracy added. Why can''t named parameters just go
> something like this:
>
> def method(param1)
> end
>
> method(:param1 = "value")
>
> ....and just accept parameters as normal, except when the first named
> parameter is encountered, assume the remaining parameters sent from a
> call are out-of-order and will also be named parameters. In other
> words, handle it transparently to the method, backwards-compatible with
> existing code and without a new non-letter-character being used to
> denote a syntax idiom.

I agree with Sean. The exception would be that the last
parameter can be a block as usual.

Hal

Sean O'Dell

9/7/2003 11:35:00 PM

Hal Fulton wrote:
> Sean O''Dell wrote:
>
>> Jeff Mitchell wrote:
>>
>>> nobu.nokada@softhome.net wrote in message
>>> news:<200309071005.h87A5o4D004546@sharui.nakada.kanuma.tochigi.jp>...
>>>
>>>>> To summerize, "%" gets us two things
>>>>>
>>>>> (1) a nice signal to let everyone know a named parameter hash is
>>>>> there
>>>>>
>>>>> (2) the ability to mix variable-length arguments with named
>>>>> parameters (in a nice way)
>>>>
>>>>
>>>>
>>>> IIRC, matz has thought ** for it.
>>>
>>>
>>>
>>>
>>> Can you give a link to this discussion? I haven''t been able to find
>>> it on google, rubygarden, etc.
>>
>>
>>
>> If it''s possible, I would prefer that Ruby DOESN''T get another
>> #$%^-style idiosyncracy added. Why can''t named parameters just go
>> something like this:
>>
>> def method(param1)
>> end
>>
>> method(:param1 = "value")
>>
>> ....and just accept parameters as normal, except when the first named
>> parameter is encountered, assume the remaining parameters sent from a
>> call are out-of-order and will also be named parameters. In other
>> words, handle it transparently to the method, backwards-compatible
>> with existing code and without a new non-letter-character being used
>> to denote a syntax idiom.
>
>
> I agree with Sean. The exception would be that the last
> parameter can be a block as usual.

Another idea occurred to me:

Could a "calling context" be prepared as an object, which allows you to
set parameters as methods and then "make the call" in one atomic action?
By this I mean, the code could do something like:

something = "this is a string"
call = Call.new(something, :slice)
call.params["pattern"] = /is/
call.call()
print call.result

I think right now I could do that as a C extension object, except I am
unsure of how to determine the order I should pass in the parameters to
String::slice. If the parameter names that slice expects are somehow
determinable, this would be cake.

If done as an extension to the Proc object, the environment when the
Call object was created could be saved as well, just like a Proc object.

Or perhaps even just extend the Method object to do this.

Hmm ...

Sean O''Dell

nobu.nokada

9/8/2003 2:08:00 AM

Hi,

At Mon, 8 Sep 2003 08:36:57 +0900,
"Sean O''Dell" <sean@cSePlsoAfMt.com[REMOVE_THE_SPAM]> wrote:
> >>> Can you give a link to this discussion? I haven''t been able to find
> >>> it on google, rubygarden, etc.

Since Excite translation service was very funny, although I
tried, excuse bad translation.

[ruby-dev:8372] Re: keyword ( or hash ) argument
# answering the question how to write a method definition has
# keyword arguments.
| It is same as Python. That is, optional arguments become
| keyword arguments. And, you can get a Hash like Symbol =>
| value with **.
|
| Suppose
|
| def foo(a=4, b=5, c=6, **keys)
| end
|
| and by invoking as foo(a: 1, d: 7, k: 44), you''ll get
|
| a=1, b=5, c=6, keys = {:d=>7, :k => 44}
|
| Unless there is **, undefined keywords occur error.

> Could a "calling context" be prepared as an object, which allows you to
> set parameters as methods and then "make the call" in one atomic action?
> By this I mean, the code could do something like:
>
> something = "this is a string"
> call = Call.new(something, :slice)
> call.params["pattern"] = /is/
> call.call()
> print call.result

What about this?

module Kernel
def calling(meth, *args)
meth = method(meth)
Proc.new {meth.call(*args)}
end
end
p "this is a string".calling(:slice, /is/).call

--
Nobu Nakada

dagbrown

9/9/2003 7:37:00 PM

In article <200309071005.h87A5o4D004546@sharui.nakada.kanuma.tochigi.jp>,
<nobu.nokada@softhome.net> wrote:
: At Sun, 7 Sep 2003 04:13:18 +0900,
: Jeff Mitchell wrote:
: > def foo3(%what_is_this)
: > # ...
: > end
: >
: > Aha there''s a percent sign so we know it''s a hash.
:
: Why does a percent sign mean a hash?

Because it means a hash in Perl.

--Dave

comp.lang.ruby

proposal for a named parameter prefix

quixoticsycophant

nobu.nokada

quixoticsycophant

quixoticsycophant

Sean O'Dell

Hal E. Fulton

Sean O'Dell

nobu.nokada

dagbrown

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