[Feature:trunk] nested loop construct

Ruby Development
1

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nphi.times do |j|
  ntheta.times do |i|

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nloop(nphi, ntheta) do |j,i|

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Yukihiro M. wrote::

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e$B$?$a$K!$$C$F$N$O$"$s$^$je(B Ruby
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e$B$"$H!$e(B[ruby-dev:38058] e$B$KJV;v2<$5$$!%e(B

3

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In message “Re: [ruby-dev:38081] Re: [Feature:trunk] nested loop
construct”
on Thu, 26 Feb 2009 03:43:31 +0900, SASADA Koichi [email protected]
writes:

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[email protected]$,9b$1$l$PH?BP$O$7$^$;$s!#$G$b<+J,$G$d$k$N$O!";d$N<j$Ke(B
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|e$B;XE&$5$l$?$N$G!$6aF|Cf$K$d$m$&$H;W$$$^$9!%e(B

e$B4|BT$7$F$^$9!#e(B

|> nloop(nphi, ntheta) do |j,i|
|>
|> e$B$H$$$&$h$&$K=q$1$?$i!“$h$j$o$+$j$d$9$/!”$+$D!"$d$d9bB.$J$N$Ge(B
|> e$B$O$J$$$+$H9M$($^$7$?!#<B:]$K<BAu$7$?$H$3$m!“e(BAO Benche$B$G$Oe(B5%e$BDxe(B
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|
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|> e$B8~$,$“$k$N$G8z2L$,$”$C$?$,!“$h$j%V%m%C%/8F$S=P$7$,7ZNL$Ke(B
|> e$B$J$l$PITMW$G$O$J$$$+e(B
|
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4

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In message “Re: [ruby-dev:38083] Re: [Feature:trunk] nested loop
construct”
on Thu, 26 Feb 2009 04:00:11 +0900, Yukihiro M.
[email protected] writes:

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|
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e$B$bDcB.$G$7$?!#e(B

e$B%*%j%8%J%ke(B: 262e$BICe(B
nloop(Ce$BHGe(B): 249e$BICe(B
nloop(Ruby): 375e$BICe(B

e$B%V%m%C%/8F$S=P$7$Oe(BRubye$B$+$i$NJ}$,B.$$$N$G$9$,!"$=$l$h$j$b%a%=%Ce(B
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e$B$;$$$+$b$7$l$^$;$se(B

def nloop(*args, &block)
helper = ->(args, buf, offset, block) {
limit = args[offset]
if (offset+1 == args.size)
limit.times do|i|
buf[offset] = i
block.yield *buf
end
else
limit.times do|i|
buf[offset] = i
helper.(args, buf, offset+1, block)
end
end
}
helper.(args, [], 0, block)
end

5

Yukihiro M. wrote::

    buf[offset] = i
    helper.(args, buf, offset+1, block)
  end
end

}
helper.(args, [], 0, block)
end

e$B!!$&$o!<!$$O$8$a$F$_$^$7$?!%e(B -> e$B$H$+e(B .() e$B$H$+!%e(B

def nloop *args
str = ‘’
h = lambda{|i|
next “yield #{(0…i).map{|e| “v#{e}”}.join(’, ')}\n”
if args.length == 0

str << "v#{i} = 0; while v#{i} < #{args.shift}\n"
str << h.call(i+1)
str << "v#{i} = v#{i}.succ;end\n"
''

}
h.call(0)
eval(str)
end

require ‘benchmark’
max = 10000
Benchmark.bm{|x|
x.report{
max.times{|i|
max.times{|j|
}
}
}
x.report{
nloop(max, max){|i, j|
}
}
}

ruby 1.9.1p0 (2009-02-02 revision 21960) [i386-mswin32_90]
t.rb:12: warning: useless use of a variable in void context
user system total real
15.039000 0.000000 15.039000 ( 13.957000)
12.105000 0.031000 12.136000 ( 11.492000)

ruby 1.8.7 (2008-12-11 revision 20371) [i386-mswin32_90]
t.rb:12: warning: useless use of a variable in void context
user system total real
10.671000 0.016000 10.687000 ( 10.642000)
t.rb:13:in nloop': (eval):3:innloop’: no block given (LocalJumpError)
from t.rb:26:in eval' from t.rb:13:innloop’
from t.rb:26
from c:/tmp/ruby_1_8/lib/ruby/1.8/benchmark.rb:293:in measure' from c:/tmp/ruby_1_8/lib/ruby/1.8/benchmark.rb:380:inreport’
from t.rb:25
from c:/tmp/ruby_1_8/lib/ruby/1.8/benchmark.rb:177:in benchmark' from c:/tmp/ruby_1_8/lib/ruby/1.8/benchmark.rb:207:inbm’
from t.rb:18

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Debian etch/amd64

ruby 1.9.2dev (2009-02-26 trunk 22636) [x86_64-linux]
user system total real
7.840000 0.000000 7.840000 ( 7.836987)
7.900000 0.000000 7.900000 ( 7.900081)

ruby 1.8.5 (2006-08-25) [x86_64-linux]
user system total real
30.340000 12.900000 43.240000 ( 43.247637)
…/trunk/test.rb:8:in <<': can't convert nil into String (TypeError) from ../trunk/test.rb:8:innloop’
from …/trunk/test.rb:8:in call' from ../trunk/test.rb:8:innloop’
from …/trunk/test.rb:12:in call' from ../trunk/test.rb:12:innloop’
from …/trunk/test.rb:26
from /usr/lib/ruby/1.8/benchmark.rb:293:in measure' from /usr/lib/ruby/1.8/benchmark.rb:377:inreport’
from …/trunk/test.rb:25
from /usr/lib/ruby/1.8/benchmark.rb:177:in benchmark' from /usr/lib/ruby/1.8/benchmark.rb:207:inbm’
from …/trunk/test.rb:18

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6

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In message “Re: [ruby-dev:38085] Re: [Feature:trunk] nested loop
construct”
on Thu, 26 Feb 2009 05:16:41 +0900, SASADA Koichi [email protected]
writes:

|ruby 1.9.1p0 (2009-02-02 revision 21960) [i386-mswin32_90]
|t.rb:12: warning: useless use of a variable in void context
| user system total real
| 15.039000 0.000000 15.039000 ( 13.957000)
| 12.105000 0.031000 12.136000 ( 11.492000)

e$B<j85$G<B9T$7$?$i$3$s$J46$8$G$7$?!#e(B

ruby 1.9.2dev (2009-02-25 trunk 22621) [i686-linux]
user system total real
8.920000 0.020000 8.940000 ( 9.038252) # while
9.440000 0.000000 9.440000 ( 9.791861) # Ce$BHGe(B
10.270000 0.010000 10.280000 ( 10.388291) # e$B$5$5$@HGe(B
43.400000 0.080000 43.480000 ( 43.973651) # e$B$^$D$b$HHGe(B

e$B4X?tE*%W%m%0%i%_%s%0CY$9$.!#$5$i$KN^L!#e(B

|ruby 1.8.7 (2008-12-11 revision 20371) [i386-mswin32_90]
|t.rb:12: warning: useless use of a variable in void context
| user system total real
| 10.671000 0.016000 10.687000 ( 10.642000)
|t.rb:13:in nloop': (eval):3:in nloop’: no block given (LocalJumpError)
| from t.rb:26:in eval' | from t.rb:13:in nloop’
| from t.rb:26
| from c:/tmp/ruby_1_8/lib/ruby/1.8/benchmark.rb:293:in measure' | from c:/tmp/ruby_1_8/lib/ruby/1.8/benchmark.rb:380:in report’
| from t.rb:25
| from c:/tmp/ruby_1_8/lib/ruby/1.8/benchmark.rb:177:in benchmark' | from c:/tmp/ruby_1_8/lib/ruby/1.8/benchmark.rb:207:in bm’
| from t.rb:18
|
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def doo
eval(“yield 42”)
end
doo{|x| p x} # => 42

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7

Yuguie$B$G$9!#e(B

On 2/26/09 3:33 AM, Yukihiro M. wrote:

e$B8!F$;v9`$Oe(B

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nphi.product(ntheta).each {} e$B$de(B
(nphi * ntheta).each {}

e$B$H$$$&$N$O$I$&$G$9$+e(B?e$B!!Hs>o$KD>46E*$@$H46$8$^$9!#e(B

8

e$B?\F#$G$9!#e(B

In [email protected]
“[ruby-dev:38095] Re: [Feature:trunk] nested loop construct” on Thu,
26 Feb 2009 17:18:15 +0900,
“Akinori MUSHA” [email protected] wrote:

v.product(*vs)

e$B$H!V<g!W$rN)$F$J$$$H$$$1$J$$$N$,$I$&$b5$$KF~$i$J$$$s$G$9$h$M!#e(B

e$B!VBP>]$H$9$ke(Bve$BA4BN!W$,!V<g!W$C$]$$5$$,$9$k$N$G!"e(B
[v1, v2, v3].product
e$B$,$$$$$J$!$H;W$$$^$7$?!#e(B

9

At Thu, 26 Feb 2009 14:52:05 +0900,
Yugui wrote:

On 2/26/09 3:33 AM, Yukihiro M. wrote:

æ¤œè¨Žäº‹é …ã¯

  • 名前。今回はnested loopということでnloopという名前で実装
    したが、もっと適切な名前があるかもしれない。妙な短縮形よ
    りも長くても記述的な名前を好む人も多いかも。Ruby(というか
    私)は前者を好む傾向はあるけど

Array#productがカルテシアン積なので、それに合わせてEnumerator#productで

nphi.product(ntheta).each {} ã‚„

　インスタンスメソッド形式は、(Array#zip 等でも感じることですが)
3つ以上あるときに、本来対等な関係にも関わらず

v1.product(v2, v3)

とか

v, *vs = *vectors
v.product(*vs)

と「主」を立てないといけないのがどうも気に入らないんですよね。

　その点、こちらは記法としては美しいと思います:

(nphi * ntheta).each {}

しかし、 Enumerable の演算子とするのは現実的に不可能(Array#* 等と
衝突する)なので、結局は各オペランドを to_enum (each) してから演算
せざるを得ず、演算するため(だけ)にわざわざ変換するというのはやや
ä½¿ã„å‹æ‰‹ã«æ¬ ã‘ã‚‹å°è±¡ãŒã‚ã‚Šã¾ã™ã€‚

　Enumerator のクラスメソッドで実装するのはどうでしょうか。

class << Enumerator
def product(*enums)
return to_enum(method, *enums) unless block_given?

return nil if enums.empty?

e, *es = *enums

if es.empty?
  e.each { |x|
    yield [x]
  }
else
  e.each { |x|
    product(*es) { |xs|
      yield [x, *xs]
    }
  }
end

nil

end

alias nest product
end

Enumerator.nest(1…3, ‘a’…‘c’, [true, false]) { |x|
p x
}

　もし簡潔さにこだわるなら、 {Class,Module}#* は今後ないだろうと
見切って alias * product してしまえば

Enumerator.*(1…3, ‘a’…‘c’, [true, false]) { |x|
p x
}

と書けますね…。

　ただ、演算子を導入し始めると、類推や一貫性への期待から次々と
新しい提案がなされ、利便性と理論的整合性の間で苦しみ続けることに
なるのではないかという懸念も持っています。
(cf. Feature #709 [ruby-core:19681])

　なお、他に思いついたクラスメソッドは

Enumerator.transpose (synchronize)
Enumerator.join (<< or +)

などです。(前者は generator ライブラリの SyncEnumerator と同等)

10

e$B$^$D$b$He(B e$B$f$-$R$m$G$9e(B

In message “Re: [ruby-dev:38094] Re: [Feature:trunk] nested loop
construct”
on Thu, 26 Feb 2009 14:52:05 +0900, “Yugui (Yuki S.)”
[email protected] writes:

|Array#producte$B$,%+%k%F%7%“%s@Q$J$N$G!”$=$l$K9g$o$;$Fe(BEnumerator#producte$B$Ge(B
|
|nphi.product(ntheta).each {} e$B$de(B
|(nphi * ntheta).each {}
|
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