Feature #3131
closedadd Kernel#Hash() method like Kernel#Array()
Description
=begin
Hello,
There is an imbalance of power in the Ruby core API (when it comes
to arrays and hashes) because it is easier to convert nil values
into empty arrays, thanks to Kernel#Array(), than it is to convert
nil values into empty hashes, due to lack of Kernel#Hash().
To correct this asymmetry and restore a balance of power, please
add a Kernel#Hash() method for converting nil, Array, and Hash
values into hashes:
module Kernel
def Hash(value)
if value.respond_to? :to_hash
value.to_hash
elsif value.respond_to? :to_ary
Hash[*value.to_ary]
elsif value.nil?
{}
else
raise ArgumentError, "invalid value for Hash: #{value}"
end
end
end
For example, here is how I would use the above API:
#-------------------------------------------------------------------------
# CASE 1: to_hash
#-------------------------------------------------------------------------
real_hash = {:real => true}
Hash(real_hash) # => {:real=>true}
fake_hash = Object.new
def fake_hash.to_hash
{:fake => true}
end
Hash(fake_hash) # => {:fake=>true}
#-------------------------------------------------------------------------
# CASE 2: to_ary
#-------------------------------------------------------------------------
real_array = [:real, true]
Hash(real_array) # => {:real=>true}
fake_array = Object.new
def fake_array.to_ary
[:fake, true]
end
Hash(fake_array) # => {:fake=>true}
#-------------------------------------------------------------------------
# CASE 3: nil
#-------------------------------------------------------------------------
Hash(nil) # => {}
#-------------------------------------------------------------------------
# CASE 4: unsupported arguments
#-------------------------------------------------------------------------
>> Hash(true)
ArgumentError: invalid value for Hash: true
from (irb):74:in `Hash'
from (irb):80
from /usr/bin/irb:12:in `<main>'
>> Hash(false)
ArgumentError: invalid value for Hash: false
from (irb):74:in `Hash'
from (irb):81
from /usr/bin/irb:12:in `<main>'
>> Hash(123)
ArgumentError: invalid value for Hash: 123
from (irb):74:in `Hash'
from (irb):82
from /usr/bin/irb:12:in `<main>'
Thanks for your consideration.
=end
Files
Updated by sunaku (Suraj Kurapati) over 14 years ago
=begin
I forgot to show that case 2 supports empty arrays:
Hash([])
=> {}
Just like Kernel#Array() supports empty hashes:
Array({})
=> []
Thanks for your consideration. And sorry for the noise.
=end
Updated by matz (Yukihiro Matsumoto) over 14 years ago
=begin
Hi,
In message "Re: [ruby-core:29462] [Feature #3131] add Kernel#Hash() method like Kernel#Array()"
on Mon, 12 Apr 2010 08:32:52 +0900, Suraj Kurapati redmine@ruby-lang.org writes:
|There is an imbalance of power in the Ruby core API (when it comes
|to arrays and hashes) because it is easier to convert nil values
|into empty arrays, thanks to Kernel#Array(), than it is to convert
|nil values into empty hashes, due to lack of Kernel#Hash().
Having Hash() might be a good idea. But since conversion from
arrays only meaningful for specific case (array of 2-element arrays),
I am not sure whether Hash() should support conversion from Array in
general or not.
matz.
=end
Updated by sunaku (Suraj Kurapati) over 14 years ago
=begin
Hi,
matz wrote:
since conversion from arrays only meaningful for specific case
(array of 2-element arrays), I am not sure whether Hash() should
support conversion from Array in general or not.
Hash::[] does not support conversion from odd-length Array (because
it is uncertain what Ruby must do with the 2n+1'th element) and will
raise an error in such case. So, in my view, Kernel#Hash() need not
support conversion from odd-length Array either.
If you wish to avoid even-length Array conversion in Kernel#Hash()
because odd-length Array conversion is not supported, then I request
that Kernel#Hash() must still support conversion from empty Array
because Kernel#Array() already supports conversion from empty Hash:
Array({})
=> []
In summary, I request that Kernel#Hash() supports conversion from:
- nil
- Hash
- empty Array
It would be nice if Kernel#Hash() also supports conversion from:
- even-length Array
Thanks for your consideration.
=end
Updated by sunaku (Suraj Kurapati) over 14 years ago
=begin
Hi,
Please allow me to clarify.
Suraj Kurapati wrote:
Hash::[] does not support conversion from odd-length Array (because
it is uncertain what Ruby must do with the 2n+1'th element) and will
raise an error in such case.
I was referring to this particular behavior:
Hash[1,2,3,4,5,6]
=> {1=>2, 3=>4, 5=>6}
Hash[1,2,3,4,5,6,7]
ArgumentError: odd number of arguments for Hash
from (irb):3:in[]' from (irb):3 from /usr/bin/irb:12:in
'
I forgot that Hash::[] can convert Array of 2-element Array into Hash:
Hash[1,2,3,4,[5,6],[7]] # non 2-element Array ignored
=> {1=>2, 3=>4, [5, 6]=>[7]}
Hash[[1,2,3,4,[5,6],[7]]] # implicit pair value is nil
=> {5=>6, 7=>nil}
Hash[[1,2,3,4,[5,6],[7,8],[7]]] # previous pair is overwritten
=> {5=>6, 7=>nil}
Thanks for your consideration.
=end
Updated by sunaku (Suraj Kurapati) over 14 years ago
=begin
Hi Matz,
To avoid delaying this request forever due to unnecessary features,
I have narrowed the requirements for Kernel#Hash() to the following:
Hash() must convert (1) nil, (2) Hash, and (3) empty Array into Hash.
module Kernel
def Hash(value)
if value.respond_to? :to_hash
value.to_hash
elsif value.nil? or Array(value).empty?
{}
else
raise ArgumentError, "invalid value for Hash: #{value}"
end
end
end
Thanks for your consideration.
=end
Updated by matz (Yukihiro Matsumoto) over 14 years ago
=begin
Hi,
In message "Re: [ruby-core:29644] [Feature #3131] add Kernel#Hash() method like Kernel#Array()"
on Tue, 20 Apr 2010 13:36:00 +0900, Suraj Kurapati redmine@ruby-lang.org writes:
|To avoid delaying this request forever due to unnecessary features,
|I have narrowed the requirements for Kernel#Hash() to the following:
|
|Hash() must convert (1) nil, (2) Hash, and (3) empty Array into Hash.
Sounds reasonable. But the new feature window for 1.9.2 was closed.
So, I will consider (positively) adding this feature after 1.9.2 release.
matz.
=end
Updated by shyouhei (Shyouhei Urabe) over 14 years ago
- Status changed from Open to Assigned
- Assignee set to matz (Yukihiro Matsumoto)
=begin
=end
Updated by sunaku (Suraj Kurapati) over 14 years ago
=begin
Hi,
Matz wrote:
I will consider (positively) adding this feature after 1.9.2
release.
Thanks Matz! In the mean time, I have created a gem with this
functionality so that people can start using it, if they wish:
http://rubygems.org/gems/kernel_hash
The source code (and unit tests) is available here:
http://github.com/sunaku/kernel_hash
Cheers.
=end
Updated by sunaku (Suraj Kurapati) about 14 years ago
=begin
Hi,
Please set the "Done %" for this issue to 80%.
The remaining 20% is for (possibly) rewriting
my proposed Kernel#Hash() Ruby code in C.
Thanks for your consideration.
=end
Updated by runpaint (Run Paint Run Run) almost 14 years ago
- File kernel-hash.patch kernel-hash.patch added
=begin
I believe the attached patch reflects the consensus between matz and Suraj. The only material difference is that a TypeError is raised instead of an ArgumentError for consistency with Integer(), Float(), etc.
=end
Updated by sunaku (Suraj Kurapati) over 13 years ago
=begin
Integer() and Float() in Ruby 1.9.2 raise TypeError and ArgumentError:
$ irb
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]¶
Float(nil)
TypeError: can't convert nil into Float
from (irb):6:inFloat' from (irb):6 from /usr/bin/irb:12:in
'
Float('meow')
ArgumentError: invalid value for Float(): "meow"
from (irb):8:inFloat' from (irb):8 from /usr/bin/irb:12:in
'
I don't know which error type we should raise in Kernel#Hash().
=end
Updated by matz (Yukihiro Matsumoto) over 13 years ago
=begin
Hi,
In message "Re: [ruby-core:35857] [Ruby 1.9 - Feature #3131] add Kernel#Hash() method like Kernel#Array()"
on Sat, 23 Apr 2011 08:52:12 +0900, Suraj Kurapati sunaku@gmail.com writes:
|Integer() and Float() in Ruby 1.9.2 raise TypeError and ArgumentError:
I think they should raise TypeError, if incompatibly here is not an
issue, I will fix.
matz.
=end
Updated by sunaku (Suraj Kurapati) almost 13 years ago
Any chance of this getting into Ruby 1.9.3? Thanks.
Updated by yeban (Anurag Priyam) almost 13 years ago
On Mon, Sep 26, 2011 at 1:52 AM, Suraj Kurapati sunaku@gmail.com wrote:
Issue #3131 has been updated by Suraj Kurapati.
Any chance of this getting into Ruby 1.9.3? Â Thanks.
Doesn't look like it. See ruby-core 39693.
--
Anurag Priyam
Updated by sunaku (Suraj Kurapati) almost 13 years ago
Thanks for the pointer. I'll just wait for Ruby 1.9.4 then.
Updated by matz (Yukihiro Matsumoto) over 12 years ago
I accept this patch for trunk, except that Hash(nil) should return an empty hash, not nil.
Matz.
Updated by ko1 (Koichi Sasada) over 12 years ago
Who should work on it?
Updated by naruse (Yui NARUSE) over 12 years ago
- Status changed from Assigned to Closed
This has already done, only missed to close.