Confusion Over Keyword Arguments

ruby-talk
1

Second one.

Dan

···

-----Original Message-----
From: ara.t.howard@noaa.gov [mailto:ara.t.howard@noaa.gov]
Sent: Thursday, March 02, 2006 9:05 AM
To: ruby-talk ML
Subject: Re: Confusion Over Keyword Arguments

On Fri, 3 Mar 2006, Berger, Daniel wrote:

>> -----Original Message-----
>> From: Yukihiro Matsumoto [mailto:matz@ruby-lang.org]
>> Sent: Wednesday, March 01, 2006 4:46 PM
>> To: ruby-talk ML
>> Subject: Re: Confusion Over Keyword Arguments
>
> <snip>
>
>> >How about "=" for keyword arguments instead
>> >(such as in python)?
>>
>> Unfortunately, assignments are legal in argument list in Ruby.
>>
>> matz.
>
> That can be made to work, with the understanding that '='
in a method
> call means 'keyword argument', not 'assignment', since there is no
> point in doing an assignment in a method call.
>
> # Method definition, '=' means assignment (of default value): def
> foo(bar, baz = 3)
> ...
> end
>
> # Method call, '=' means keyword
> foo(baz = 5, bar = 2)

but is

   foo baz = 5, bar = 2

   a, b = foo(baz = 5), (bar = 2)

or

   a = foo( (baz = 5), (bar = 2) )

??

2

but that's a problem no? number two is the same as this

   baz = 5
   bar = 2
   a = foo baz, bar

see, when on writes

   foo baz = 5, bar = 2

it's ambiguous if those assignments are part of a method call or not. bar
escpecitally, it could easily be considered an assignment statement (bar=2)
that's part of a parrallel assignment statement.

or am i missing something?

-a

···

On Fri, 3 Mar 2006, Berger, Daniel wrote:

# Method definition, '=' means assignment (of default value): def
foo(bar, baz = 3)
  ...
end

# Method call, '=' means keyword
foo(baz = 5, bar = 2)

but is

   foo baz = 5, bar = 2

   a, b = foo(baz = 5), (bar = 2)

or

   a = foo( (baz = 5), (bar = 2) )

??

Second one.

--
judge your success by what you had to give up in order to get it.
- h.h. the 14th dali lama

3

# Method definition, '=' means assignment (of default value): def
foo(bar, baz = 3)
  ...
end

# Method call, '=' means keyword
foo(baz = 5, bar = 2)

but is

   foo baz = 5, bar = 2

   a, b = foo(baz = 5), (bar = 2)

or

   a = foo( (baz = 5), (bar = 2) )

??

Second one.

but that's a problem no? number two is the same as this

  baz = 5
  bar = 2
  a = foo baz, bar

No, then they become positional. That's the same as foo 2, 5.

see, when on writes

  foo baz = 5, bar = 2

it's ambiguous if those assignments are part of a method call or not. bar
escpecitally, it could easily be considered an assignment statement (bar=2)
that's part of a parrallel assignment statement.

or am i missing something?

The parser just has to be trained well enough. :slight_smile:

That being said, perhaps using '=' as a keyword operator would just cause too much confusion amongst the Ruby community. I know some people hate changing behavior based on context.

Regards,

Dan

···

ara.t.howard@noaa.gov wrote:

On Fri, 3 Mar 2006, Berger, Daniel wrote: