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From: Harry Kakueki on 20 Jul 2010 11:26
On Tue, Jul 20, 2010 at 11:25 PM, Vitaliy Yanchuk <fuksito(a)gmail.com> wrote:
> Jean-Julien Fleck, thanks.
> Maybe have an idea of a one-line version? :)
>

Try this or something like this.
I'm very sleepy ZZZZZZZZZZZ




arr = ["a", "b", "a", "c", "c", "b", "b"]
p Hash[*(arr.uniq.map{|x| [x,arr.select{|y| y == x}.length]}).flatten]

#> {"a"=>2, "b"=>3, "c"=>2}


Harry

From: Colin Bartlett on 20 Jul 2010 11:32
[Note: parts of this message were removed to make it a legal post.]

On Tue, Jul 20, 2010 at 2:47 PM, Vitaliy Yanchuk <fuksito(a)gmail.com> wrote:

> ... Would be grateful if someone can tell, how can I do shortly (mb with
> one
> method) from such example array
> ["a", "b", "a", "c", "c", "b", "b"]
> The result: a => 2, b => 3, c => 2. So, to count number of occurances.


def owtdi( ary ); h = Hash.new(0); ary.each {|e| h[e] += 1}; h; end
def owtdi2( ary ); ary.inject(Hash.new(0)) {|h,e| h[e]+= 1; h}; end

def tmtowtdi( ary )
ary = ary.sort; test_v = ! ary[0]; cary = []; kt = nil
ary.each do |vv|
if vv != test_v then
cary << [test_v, kt] if kt
test_v = vv; kt = 0
end
kt += 1
end
cary << [test_v, kt] if kt
cary
end

rr = ["a", "b", "a", "c", "c", "b", "b"]
p owtdi( rr ), owtdi2( rr ), tmtowtdi( rr )
kt = 100_000
require "benchmark"
ow = ow2 = tmtow = nil
Benchmark.bmbm do|b|
b.report("owtdi") { kt.times { ow = owtdi( rr ) } }
b.report("tmtowtdi") { kt.times { tmtow = tmtowtdi( rr ) } }
end
puts; p ow, tmtow
__END__
{"a"=>2, "b"=>3, "c"=>2}
[["a", 2], ["b", 3], ["c", 2]]

user system total real
ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
owtdi 3.572000 0.016000 3.588000 ( 4.422000)
tmtowtdi 4.883000 0.031000 4.914000 ( 5.819000)

ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32]
owtdi 2.558000 0.047000 2.605000 ( 3.243000)
tmtowtdi 1.545000 0.015000 1.560000 ( 1.943000)
another 1.9.1 run: owtdi user = 2.293 and tmtowtdi user = 1.810;

jruby 1.5.0.RC1 (ruby 1.8.7 patchlevel 249) (2010-04-14 0b08bc7)
(Java HotSpot(TM) Client VM 1.6.0_14) [x86-java]
owtdi 1.980000 0.000000 1.980000 ( 1.979000)
tmtowtdi 1.523000 0.000000 1.523000 ( 1.522000)
I ought to point out that in a subsequent JRuby run
owtdi user = 1.625 and tmtowtdi user = 1.809,
and in another run owtdi user = 2.118 and tmtowtdi user = 1.987,
so quite variable! But there was quite a lot of apparently random and
purposeless disk i/o going on while the benchmarks were running. (Thank you,
Windows Vista!) So I would place even less reliance than usual on these
benchmarks. But using inject does seem significantly slower, especially so
using 1.8.6.

From: Jean-Julien Fleck on 20 Jul 2010 11:41
2010/7/20 Harry Kakueki <list.push(a)gmail.com>:
> p Hash[*(arr.uniq.map{|x| [x,arr.select{|y| y == x}.length]}).flatten]

Harry showed the way:

>> Hash[arr.group_by {|o| o}.collect{|k,v| [k,v.size]}]
=> {"a"=>2, "b"=>3, "c"=>2}

Cheers,

--
JJ Fleck
PCSI1 Lycée Kléber

From: Vitaliy Yanchuk on 20 Jul 2010 15:28
Check this out

['a', 'b', 'a', 'b', 'c', 'c',
'c'].group_by{|o|o}.collect{|k,v|{k,v.size}}.to_yaml"

Result:
- a: 2
- b: 2
- c: 3


--
Posted via http://www.ruby-forum.com/.

From: David A. Black on 20 Jul 2010 16:56
Hi --

On Wed, 21 Jul 2010, Vitaliy Yanchuk wrote:

> Rob Biedenharn wrote:
>> Soo... that has a semi-colon and isn't then a one-liner?? ;-)
>
> Yeah, not perfectly one-liner. But it is without dot-chain breaking, not
> bad too :)

In Ruby 1.9 there's Enumerator#with_object, which is a nice way to avoid
that "; h" thing that you have to do in #inject to make it return the
accumulator:

count_hash = a.each.with_object(Hash.new(0)) {|e, hash| hash[e] += 1 }


David

--
David A. Black, Senior Developer, Cyrus Innovation Inc.

The Ruby training with Black/Brown/McAnally
Compleat Philadelphia, PA, October 1-2, 2010
Rubyist http://www.compleatrubyist.com

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