読めるかな？ちょっとレアなRubyの記法

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Tomokazu Kiyohara 2025/01/18(Sat) ๺཮ࡾݝ.rb Lightning Talks in Kanazawa ಡΊΔ͔ͳʁ ͪΐͬͱϨΞͳRubyͷه๏

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🎉 Ruby 3.4 released at ’24/12/25

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৽ه๏ it

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it is "default block parameter" ref. Fe a ture #18980: `it` a s a def a ult block p a r a meter - Ruby m a ster - Ruby Issue Tr a cking System ( https://bugs.ruby-l a ng.org/issues/18980 )

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ϒϩοΫύϥϝʔλ [1, 2, 3].map {|i| i * 10 } #=> [ 10, 20, 30 ]

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ϒϩοΫύϥϝʔλ [1, 2, 3].map {|i| i * 10 } #=> [ 10, 20, 30 ]

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"σϑΥϧτ" ϒϩοΫύϥϝʔλ [1, 2, 3].map {|i| i * 10 } [1, 2, 3].map { it * 10 } #=> [ 10, 20, 30 ]

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"σϑΥϧτ" ϒϩοΫύϥϝʔλ [1, 2, 3].map {|i| i * 10 } [1, 2, 3].map { it * 10 } #=> [ 10, 20, 30 ]

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it ͝࢖༻্ͷ஫ҙʹ͍ͭͯ

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it ͝࢖༻্ͷ஫ҙʹ͍ͭͯ [1, 2, 3].map { it * 10 } #=> [ 10, 20, 30 ] it = 9 [1, 2, 3].map { it * 10 } #=> [ 90, 90, 90 ] ϒϩοΫ֎Ͱ it Λఆ͍ٛͯ͠Δͱ ϒϩοΫ಺ͷ it ͸౰֘ม਺ͱͯ͠ॲཧ͞ΕΔ

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• αϯϓϧίʔυͰΘ͔ΔʂRuby 3.4ͷओͳ৽ػೳͱมߋ఺ P a rt 2ɾ৽ ػೳͱมߋ఺ͷ૯·ͱΊ #R a ils - Qiit a • https://qiit a .com/jnchito/items/ e a db5f96e0fd ff 01bd71#%E3%83%87%E3%83%95%E3%82%A9%E3%83%AB%E3%83%88%E3%81%AE%E3 %83%96%E3%83%AD%E3%83%83%E3%82%AF%E3%83%91%E3%83%A9%E3%83%A1%E3%83%BC%E3%8 2%BF%E3%81%A8%E3%81%97%E3%81%A6-it- %E3%81%8C%E8%BF%BD%E5%8A%A0%E3%81%95%E3%82%8C%E3%81%9F • ϓϩͱಡΈղ͘Ruby 3.4 NEWS - STORES Product Blog • https://product.st.inc/entry/2024/12/25/154728 it ਂ۷Γ

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ͪͳΈʹ

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default block parameter it ͷɺ͞Βʹલ

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numbered block parameter (Ruby 2.7 ~) ref. Ruby 2.7 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/2.7.html#numbered-block-p a r a meters )

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"φϯόʔυ" ϒϩοΫύϥϝʔλ [[1,2],[10,20]].map{|a, b| a*b } #=> [ 10, 40 ] [[1,2],[10,20]].map{ _1 * _2 } #=> [ 10, 40 ]

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"φϯόʔυ" ϒϩοΫύϥϝʔλ [[1,2],[10,20]].map{|a, b| a*b } #=> [ 10, 40 ] [[1,2],[10,20]].map{ _1 * _2 } #=> [ 10, 40 ]

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it ͸ _1 ʹผ໊͕͍ͭͨ ͱ΋ݴ͑Δ ҰํͰ it ͱ _2 ΛಉҰϒϩοΫ಺ʹॻ͚ͳ͍ͱ͍ͬͨ ੍໿΋͋ͬͨΓ͢Δ

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• Ruby: "uselessγϯλοΫεγϡΨʔ"γϦʔζ: numbered block p a r a metersʢ຋༁ʣʛTechR a cho by BPSגࣜձࣾ • https://techr a cho.bpsinc.jp/h a chi8833/2024_01_22/136901 numbered block parameter ਂ۷Γ

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͍Ζ͍Ζͳॻ͖ํΛ஌͓ͬͯ͘ͱ ίʔυϨϏϡʔ΋͸͔ͲΔ ʢ͔΋͠Εͳ͍ʣ

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ͪΐͬͱϨΞͳ Ruby ͷॻ͖ํ ͍Ζ͍Ζ ʢϨΞϦςΟ͸ݸਓͷײ૝Ͱ͢ʣ

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஫ҙ ϨΞϦςΟͱ ॻ͖΍͢͞΍ಡΈ΍͢͞͸ ผ෺

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஫ҙ ࠓ೔ͷϨΞϦςΟ͸ ໌೔ʹ͸มΘ͍ͬͯ͘ ʢࠓޙͲΜͲΜݟΔΑ͏ʹͳΔ͔΋ʣ

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Let's go

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html = %Q{

} colors = %w[red blue green] regex = %r{https?://[\w.-]+} ϨΞϦςΟɿ˒

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% ه๏ ref. Ϧςϥϧ (Ruby 3.4 ϦϑΝϨϯεϚχϡΞϧ) ( https://docs.ruby-l a ng.org/j a /l a test/doc/spec=2 f liter a l.html#percent )

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% ه๏ % %Q %(a b #{1 + 2}) %Q(a b #{1 + 2}) "a b #{1 + 2}" "a b 3" %q %q(a b #{1 + 2}) 'a b #{1 + 2}' "a b \#{1 + 2}" %x %x(ls -a) `ls -a` ".\n..\n.git\nREADME\n" %r %r([A-z]+$) /[A-z]+$/ /[A-z]+$/ %w %w(a b #{1 + 2}) ['a', 'b', '#{1', '+', '2}'] ["a", "b", "\#{1", "+", "2}"] %W %W(a b #{1 + 2}) ["a", "b", "#{1 + 2}"] ["a", "b", "3"] %s %s(a b #{1 + 2}) :'a b #{1 + 2}' :"a b \#{1 + 2}" %i %i(a b #{1 + 2}) [:a, :b, :'#{', :+, :'2}'] [:a, :b, :"\#{", :+, :"2}"] %I %I(a b #{1 + 2}) [:a, :b, :"#{1 + 2}"] [:a, :b, :"3"]

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% ه๏ • ΤεέʔϓॲཧΛল͚Δͷ͕ར఺ • ॻ͖΍͢͞ͱ͍͏ΑΓ΋ಡΈ΍͢͞ • %() ͷ () ෦ʢσϦϛλʣ͸͍Ζ͍Ζͳ΋ͷʹஔ͖׵͑Մೳ • {} [] () <> # ͳͲͳͲ

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val = foo&.bar&.baz ϨΞϦςΟɿ˒

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Safe navigation operator a.k.a. ΅ͬͪԋࢉࢠ (Ruby 2.3~) ref. Fe a ture #11537: Introduce "S a fe n a vig a tion oper a tor" - Ruby m a ster - Ruby Issue Tr a cking System ( https://bugs.ruby-l a ng.org/issues/ 11537 )

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val = foo&.bar&.baz bar = foo.nil? ? nil : foo.bar val = bar.nil? ? nil : bar.baz Safe navigation operator Ϩγʔό͕ nil ͷ৔߹ ɾҾ਺ͷධՁ͕ߦͳΘΕͳ͍ ɾϝιουݺͼग़͕͠ߦΘΕͳ͍ ɾnil Λฦ͢

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foo&.bar = val unless foo.nil? foo.bar = val end Safe navigation operator ୅ೖʹ΋ར༻Մೳ

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%w[a b c].map(&:upcase) ϨΞϦςΟɿ˒˒

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SymbolProc ref. Cl a ss: RuboCop::Cop::Style::SymbolProc — Document a tion for bb a tsov/RuboCop (m a ster) ( https://www.rubydoc.info/github/bb a tsov/ RuboCop/RuboCop/Cop/Style/SymbolProc ) ref. Ruby: Ξϯύαϯυͱίϩϯ`&:`ه๏ʹ͍ͭͯௐ΂ͯΈͨʛTechR a cho by BPSגࣜձࣾ https://techr a cho.bpsinc.jp/ h a chi8833/2021_05_27/66735

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['a','b','c'].map(&:upcase) => ["A", "B", "C"] ['a','b','c'].map {|i| i.upcase} => ["A", "B", "C"] &:symbol & (Proc coercion) ͱ :symbol ͷ૊Έ߹Θͤ ʢ&: ͱ͍͏ԋࢉࢠͱ͍͏Θ͚Ͱ͸ͳ͍ʣ

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def foo(k1:, k2:, **kwrest) end # different from below # def foo(k1, k2, *rest) end ϨΞϦςΟɿ˒˒

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double splat parameter ref. Ϋϥεʗϝιουͷఆٛ (Ruby 3.4 ϦϑΝϨϯεϚχϡΞϧ) ( https://docs.ruby-l a ng.org/j a /3.4/doc/spec=2fdef.html#method )

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def foo(k1:, k2:, **kwrest) end foo(k1:'a', k2:'b', k3:'c', k4:'d') # kwrest => { k3:'c', k4:'d' } double splat parameter keyword Ҿ਺ͷʮ࢒Γશ෦ʯ *rest ͰҐஔҾ਺ͷʮ࢒Γશ෦ʯΛड͚Δͷͱ΄΅ಉ͡ def foo( a , b, *rest)

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my_hash = { v1:, v2: } val = my_func(v1:, v2:) ϨΞϦςΟɿ˒˒˒

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Hash & Keyword Ҿ਺ͷʮলུʯ (Ruby 3.1~) ref. Ruby 3.1 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/3.1.html#v a lues-in-h a sh-liter a ls- a nd-keyword- a rguments-c a n-be-omitted )

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h = { x:, y: } # { x: x, y: y } と同じ foo(x:, y:) # (x: x, y: y) と同じ Hash & Keyword Ҿ਺ͷʮলུʯ key ͱಉ໊ͷม਺ࢀর͸লུԽ puts σόοά࣌ͳͲʹ΋ศར p x:, y:

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def f(x, y) = x + y ϨΞϦςΟɿ˒˒˒

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“Endless” method de fi nition (Ruby 3.0~) ref. Ruby 3.0 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/3.0.html#endless-method-de f inition )

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def available? !@list.empty? end def available? = !@list.empty? “Endless” method de fi nition 1ߦͰؔ਺Λఆٛ

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[BASE_URL, path].join('/') .then { URI.open(it).read } .then { JSON.parse(it) } .dig('owner' ) .then { it.to_yaml } .then { File.write('out.yml', it) } ϨΞϦςΟɿ˒˒˒˒

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then ԋࢉࢠ (Ruby 2.6~) ref. Ruby 2.6 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/2.6.html#then- a s- a n- a li a s-for-yield_self )

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Ruby 2.4 Ҏલͷॻ͖ํ path = [BASE_URL, path].join('/') json = URI.open(path).read content = JSON.parse(json) owner = content.dig('owner') yaml = owner.to_yaml File.write('out.yml', yaml)

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#yield_self (Ruby 2.5~) [BASE_URL, path].join('/') .yield_self {|path| URI.open(path).read } .yield_self {|json| JSON.parse(json) } .dig('owner') .yield_self {|owner| owner.to_yaml } .yield_self {|yaml| File.write('out.yml',yaml) } ࣗ਎ΛҾ਺ʹϒϩοΫΛ࣮ߦ & ϒϩοΫͷ݁ՌΛฦ͢

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#yield_self ͷผ໊ #then [BASE_URL, path].join('/') .then {|path| URI.open(path).read } .then {|json| JSON.parse(json) } .dig('owner') .then {|owner| owner.to_yaml } .then {|yaml| File.write('out.yml',yaml) } #tap ͱ͍͏ྨࣅϝιου΋͋Δ ʢࣗ਎ΛҾ਺ʹϒϩοΫΛ࣮ߦ & ࣗ਎Λฦ͢ʣ

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it ͱͷ૊Έ߹Θͤ [BASE_URL, path].join('/') .then { URI.open(it).read } .then { JSON.parse(it) } .dig('owner' ) .then { it.to_yaml } .then { File.write('out.yml', it) }

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def wrap_f1(&) = f1(&) def wrap_f2(*) = f2(*) def wrap_f3(**) = f3(**) ϨΞϦςΟɿ˒˒˒˒˒

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Anonymous block argument (Ruby 3.1~) & Anonymous arguments passing (Ruby 3.2~) ref. Ruby 3.1 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/3.1.html# a nonymous-block- a rgument ) ref. Ruby 3.2 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/3.2.html# a nonymous- a rguments-p a ssing- improvements )

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def wrap_f1(&) = f1(&) # ブロック引数 def wrap_f2(*) = f2(*) # 全位置引数 def wrap_f3(**) = f3(**) # 全キーワード引数 def wrap_f4(*, **) f4_1(*) f4_2(**) end # こういった書き方も出来る શҾ਺Λͦͷ··ผͷϝιου΁

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if user in { name:, role: } puts %(#{name} is #{role}) end ϨΞϦςΟɿ˒˒˒˒˒˒

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Pattern matching (in) (Ruby 2.7~) ref. Ruby 2.7 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/2.7.html#p a ttern-m a tching ) ref. p a ttern_m a tching - Document a tion for Ruby 3.5 ( https://docs.ruby-l a ng.org/en/m a ster/synt a x/p a ttern_m a tching_rdoc.html )

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ύλʔϯϚονϯά • P a ttern m a tching is a fe a ture a llowing deep m a tching of structured v a lues: checking the structure a nd binding the m a tched p a rts to loc a l v a ri a bles. • ύλʔϯϚονϯά͸ωετΛؚΉσʔλߏ଄ͷϚονϯάΛՄೳʹ ͢Δػೳ • σʔλߏ଄Λ֬ೝ͢Δ (checking) • Ұகͨ͠෦෼ΛϩʔΧϧม਺ʹׂΓ౰ͯΔ (binding)

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if user in { name:, role: } puts %(#{name} is #{role}) end Pattern matching (in) in ۟ͷޙʹ Hash Λهड़͢Δ͜ͱͰ ߏ଄ͷνΣοΫͱม਺΁ͷ୅ೖΛಉ࣌ʹߦ͍ͬͯΔ ͜͜Ͱ {name:, role:} ͸লུه๏ {name:n, role:r} ͱॻ͍ͨ৔߹͸ม਺ n,r ͕ఆٛ͞ΕΔ

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user => { name:, role: } puts %(#{name} is #{role}) ϨΞϦςΟɿ˒˒˒˒˒˒

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Pattern matching (=>) (Ruby 3.0~) ref. Ruby 3.0 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/3.0.html#p a ttern-m a tching ) ref. p a ttern_m a tching - Document a tion for Ruby 3.5 ( https://docs.ruby-l a ng.org/en/m a ster/synt a x/p a ttern_m a tching_rdoc.html )

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user => { name:, role: } puts %(#{name} is #{role}) Pattern matching (=>) => ӈ୅ೖ(rightw a rd a ssignment) ߏจ ߏ଄Ϛον͠ͳ͍৔߹͸Τϥʔ͕ rise ͞ΕΔ (NoMatchingPatternKeyError ͳͲ)

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File.read('test.txt') .split("\n") .map(&:strip) .reject(&:empty?) .first(10) => lines [BASE_URL, path].join('/') .then { URI.open(it).read } .then { JSON.parse(it) } .dig('owner' ) .then { it.to_yaml } => yaml => Λ୅ೖ͚ͩͷ༻్Ͱ࢖͏͜ͱ΋ ͜Ε͸࠷ۙ ݟΔؾ͕͢Δ ϨΞϦςΟ௿Ί … ͔΋

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user => { name:, age: 13..28} puts %(#{name} is gen-Z) ϨΞϦςΟɿ˒˒˒˒˒˒

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Pattern matching (Expression) (Ruby 3.1~) ref. Ruby 3.1 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/3.1.html#p a ttern-m a tching ) ref. p a ttern_m a tching - Document a tion for Ruby 3.5 ( https://docs.ruby-l a ng.org/en/m a ster/synt a x/p a ttern_m a tching_rdoc.html )

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user => { name:, age: 13..28} puts %(#{name} is gen-Z) Pattern Matching(Expressions) ࣜΛ࢖ͬͨύλʔϯϚον ϩʔΧϧม਺Ҏ֎ͷม਺(non-loc a l v a ri a bles) Λࣜ෦ʹ࢖͏৔߹͸ ^ ۟Λ࢖ͬͨ pinning ॲཧ͕ඞཁ (ৄࡉུ) ม਺΁ͷׂΓ౰ͯ͸ߦΘΕͳ͍

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case user in role: "admin" puts "super user" in age: 13..28 puts %(#{name} is gen-Z) in name:, role: puts %(#{name} is #{role}) end ϨΞϦςΟɿ˒˒˒˒˒˒˒

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Pattern matching (case) (Ruby 3.2~) ref. Ruby 3.2 ch a nges - Ruby Ch a nges ( https://rubyreferences.github.io/rubych a nges/3.2.html#p a ttern-m a tching ) ref. p a ttern_m a tching - Document a tion for Ruby 3.5 ( https://docs.ruby-l a ng.org/en/m a ster/synt a x/p a ttern_m a tching_rdoc.html )

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case user in role: "admin" puts "super user" in age: 13..28 puts %(#{name} is gen-Z) in name:, role: puts %(#{name} is #{role}) end Pattern matching (case) case-when ߏจͱ΄΅ಉ͡

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• Ruby: "uselessγϯλοΫεγϡΨʔ"γϦʔζʮύλʔϯϚονϯά ʢ1/3ʣʯʢ຋༁ʣʛTechR a cho by BPSגࣜձࣾ • https://techr a cho.bpsinc.jp/h a chi8833/2024_01_31/138590 • ·ͩ·ͩԞਂ͍ • ΫϥεͷҰகνΣοΫͱ͔ • "Find p a ttern" value in [*, pattern, *] ͱ͔ Pattern matching ਂ۷Γ

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5.times{|n| p n if (n==2)..(n==3) } ϨΞϦςΟɿ˒˒˒˒˒˒˒˒

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fl ip- fl op ৚݅ࣜ ref. ԋࢉࢠࣜ (Ruby 3.4 ϦϑΝϨϯεϚχϡΞϧ) ( https://docs.ruby-l a ng.org/j a /l a test/doc/spec=2foper a tor.html#r a nge_cond )

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5.times{|n| p n if (n==2)..(n==3) } # => 2 # 3 fl ip- fl op ৚݅ࣜ ʮ৚݅ࣜͱͯ͠ʯൣғࣜΛهड़ͨ͠ͱ͖͚ͩͷಛघಈ࡞ "ࠨ෦Λຬͨͨ͠Βɺӈ෦Λຬͨ͢·Ͱ true" "Range ͷதʹऩ·ͬͯͨΒ" Ͱ͸ͳ͍

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[1,2,3,4,5,4,3,2,1].each{|n| p n if (n==3..) } fl ip- fl op తͳಈ࡞ྫ

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[1,2,3,4,5,4,3,2,1].each{|n| p n if (n==3..) } # => 3 # 4 # 5 # 4 # 3 # 2 ← でる # 1 ← でる fl ip- fl op తͳಈ࡞ྫ

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• ʮঢ়ଶʯΛ࣋ͭಛघͳ৚݅ࣜ • ঢ়ଶ = ॳظঢ়ଶ or ࣜ1͕Ϛονͨ͠ޙ or ࣜ2͕Ϛονͨ͠ޙ • .. ͷ৔߹ͱ ... ͷ৔߹Ͱಈ࡞͕एׯҟͳΔ • sed ΍ a wk ༝དྷͷಈ࡞ • ݸਓతʹ͸ɺ࣮ࡍʹ࢖ΘΕ͍ͯΔͱ͜ΖΛݟͨ͜ͱ͕ͳ͍ • ύʔαʔͱ͔Ͱ͔ͭΘΕ͍ͯΔΜͩΖ͏ɺͱࢥ͏ • ಈ࡞Λޡղ͠΍͍ͨ͢Ί͚͞ΒΕ͍ͯΔɺͷ͔΋ fl ip- fl op ਂ۷Γ

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break

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Ruby ʹ͸ ͍Ζ͍Ζͳॻ͖ํ͕͋Γ·͢Ͷ

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શ෦Λ࢖͍͜ͳ͢ඞཁ͸ͳ͍ ಡΊΔͱͪΐͬͱ ࣌ؒͷઅ໿ʹͳΔ͔΋

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ಡΊͳͯ͘΋ AI ʹฉ͚͹ ͓͓Αͦਖ਼͘͠ղઆͯ͘͠ΕΔ

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Happy Ruby Coding! Tomokazu Kiyohara http://github.com/kiyohara http://facebook.com/tomokazu.kiyohara