Need help to understand when should Kernel#Hash return empty hash

ruby-talk
1

As per the documentation of `Kernel#Hash`
(http://www.ruby-doc.org/core-2.0/Kernel.html#method-i-Hash)

- Returns an empty Hash when arg is nil or [].

RUBY_VERSION # => "2.0.0"

Hash[["class", "foo"]] # => {}

What happened with the below 2 cases :-

- why not empty hash `{}` ?

Hash[[["class", "foo"]]] # => {"class"=>"foo"}

- why the error ?

Hash[nil] # => # ~> -:5:in `[]': odd number of arguments for Hash
(ArgumentError)

···

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2

Hash[["class", "foo"]]
(irb):2: warning: wrong element type String at 0 (expected array)
(irb):2: warning: ignoring wrong elements is deprecated, remove them
explicitly
(irb):2: warning: this causes ArgumentError in the next release
(irb):2: warning: wrong element type String at 1 (expected array)
(irb):2: warning: ignoring wrong elements is deprecated, remove them
explicitly
(irb):2: warning: this causes ArgumentError in the next release
=> {}

Hash[*["class", "foo"]] #=> {"class"=>"foo"}

···

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3

You are not invoking Kernel#Hash here but Hash#.

robert

···

On Sat, Aug 24, 2013 at 9:59 AM, Love U Ruby <lists@ruby-forum.com> wrote:

As per the documentation of `Kernel#Hash`
(Module: Kernel (Ruby 2.0.0))

- Returns an empty Hash when arg is nil or .

RUBY_VERSION # => "2.0.0"

Hash[["class", "foo"]] # => {}

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4

Robert Klemme wrote in post #1119503:

···

On Sat, Aug 24, 2013 at 9:59 AM, Love U Ruby <lists@ruby-forum.com> > wrote:

RUBY_VERSION # => "2.0.0"

Hash[["class", "foo"]] # => {}

You are not invoking Kernel#Hash here but Hash#.

robert

@Robert - basically depending on what Kernel#Hash and Hash# methods
are switched between them?

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