Hash#values_at

[Ara.T.Howard]

what is the rational behind this?

({}.values_at :a).empty? #=> false

i would expect

({}.values_at :a) #=> nil

or

({}.values_at :a) #=> []

but not the actual

({}.values_at :a) #=> [nil]

there must be some reason for this, but i cannot see why returning an 'array
full of nothing' is preferable to returning an 'emtpy array'... is there some
way of thinking about this that will make it seem less suprising?

-a
--
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| EMAIL :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
| PHONE :: 303.497.6469
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| TRY :: for l in ruby perl;do $l -e "print \"\x3a\x2d\x29\x0a\"";done
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[Yukihiro Matsumoto]

Hi,

In message "Hash#values_at"
|
|what is the rational behind this?
|
| ({}.values_at :a).empty? #=> false
|
|i would expect
|
| ({}.values_at :a) #=> nil
|
|or
|
| ({}.values_at :a) #=> []
|
|but not the actual
|
| ({}.values_at :a) #=> [nil]
|
|there must be some reason for this, but i cannot see why returning an 'array
|full of nothing' is preferable to returning an 'emtpy array'... is there some
|way of thinking about this that will make it seem less suprising?

def values_at(*args)
args.collect do |i|
self
end
end

matz.

 

[Ara.T.Howard]

Date: Mon, 16 Feb 2004 15:33:59 +0900
From: Yukihiro Matsumoto <[email protected]>
Newsgroups: comp.lang.ruby
Subject: Re: Hash#values_at

Hi,

In message "Hash#values_at"
|
|what is the rational behind this?
|
| ({}.values_at :a).empty? #=> false
|
|i would expect
|
| ({}.values_at :a) #=> nil
|
|or
|
| ({}.values_at :a) #=> []
|
|but not the actual
|
| ({}.values_at :a) #=> [nil]
|
|there must be some reason for this, but i cannot see why returning an 'array
|full of nothing' is preferable to returning an 'emtpy array'... is there some
|way of thinking about this that will make it seem less suprising?

def values_at(*args)
args.collect do |i|
self
end
end

matz.

ah. also

irb(main):001:0> {:k=>:v}.values_at
=> []

thanks.

-a
--
===============================================================================
| EMAIL :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
| PHONE :: 303.497.6469
| ADDRESS :: E/GC2 325 Broadway, Boulder, CO 80305-3328
| URL :: http://www.ngdc.noaa.gov/stp/
| TRY :: for l in ruby perl;do $l -e "print \"\x3a\x2d\x29\x0a\"";done
===============================================================================