Why doesn't Ruby have Boolean class?

by Masafumi Okura

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ͳͥRubyʹ͸BooleanΫϥε ͕ͳ͍ͷ͔ BuriKaigi 2024 OKURA Masafumi, 2024-01-20

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BuriKaigi

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3ճ໨ͷొஃ 2020, 2022, 2024

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ࠓճͷ ݸਓత ϨΪϡϨʔγϣϯ

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Ჳʹؔ܎ͷ͋Δ τʔΫ

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Ჳ

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No content

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ϒϦ

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ϒʔϦ

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ϒʔϦΞϯ

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Boolean!

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Rubyʹ͸ BooleanΫϥε͕ ͳ͍ʂ

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ϒʔϦΞϯɿͳͥRubyʹ͸ BooleanΫϥε͕ͳ͍ͷ͔ BuriKaigi 2024 OKURA Masafumi, 2024-01-20

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ࣗݾ঺հ

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ࣗݾ঺հ • ໊લɿେ૔խ࢙ • ॴଐɿϑϦʔϥϯε • ՝֎׆ಈɿKaigi on RailsνʔϑΦʔΨφΠβʔɺOSS։ൃɺ֤छొஃ ʢEuruko, RubyConfTw, VimConf, σϒαϛ2024ʣ • ޷͖ͳݴޠͳͲɿRubyɺRailsɺNeovim • ෋ࢁྺɿ2ճ໨

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ʲະঝ୚޿ࠂཝʳ ʲ͓࢓ࣄืूʳ ʲৄࡉ͸࠙਌ձʳ

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͓඼ॻ͖

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ࠓ೔ͷ͓࿩ 1. Fact: Rubyʹ͓͚ΔBooleanͷѻ͍ʹ͍ͭͯ 2. Opinion: RubyʹBooleanΫϥε͕ͳͯ͘΋Α͍ཧ༝ʹ͍ͭͯ

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͋Εɺܕͷ࿩͸ʁ

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20෼ʹऩ·Βͳ ͔ͬͨͷͰׂѪ

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ࠓճͷτʔΫͷ ࣋ͪؼΓ ʢTakeawayʣ

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ࠓճͷτʔΫͰ࣋ͪؼͬͯ΄͍͜͠ͱ • Ruby͕ਅِ஋ؚΉΦϒδΣΫτʹରͯ͠औ͍ͬͯΔΞϓϩʔν • ʮϓϦϛςΟϒʯ͕ଘࡏ͠ͳ͍ͱ͍͏͜ͱ • ϓϩάϥϛϯάݴޠʹ͓͚ΔҙࢥܾఆͷҰྫ • BooleanΛ௥Ճ͠ͳ͍ͱ͍͏ܾఆ • ʮσβΠϯࢥߟʯ

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1. Rubyʹ͓͚Δ Booleanͷѻ͍

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Seeing Is Believing

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Rubyʹ͓͚ΔBooleanͷѻ͍ • TrueClassͱFalseClass͕ͦΕͧΕtrueͱfalseͷΫϥε • ͜ΕΒΫϥε͸newϝιουΛݺ΂ͳ͍ʢγϯάϧτϯʣ • TrueClassͱFalseClassʹ͸ڞ௨ͷ਌ΫϥεͳͲ͸ͳ͍ • to_boolͷΑ͏ͳϝιου͸ଘࡏ͠ͳ͍ʢ!!Ͱ୅༻Մೳʣ • Ifจʹ͸ͲͷΑ͏ͳΦϒδΣΫτͰ΋࢖͑ΔʢfalseͱnilҎ֎શͯtrueʣ

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ଞͷݴޠͰ͸ɺ true/false͸ଈ஋ ͔΋͠Εͳ͍

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Ұํɺ Rubyʹ͸ ଈ஋͕ͳ͍

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શͯ͸ ΦϒδΣΫτ

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શͯͷ ΦϒδΣΫτʹ Ϋϥε͕͋Δ

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ଐ͍ͯ͠Δ Πϯελϯε͕ 1͔ͭ͠ͳ͍Ϋϥε

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TrueClass FalseClass NilClass

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ศ্ٓଘࡏͯ͠ ͍Δͱ΋ݴ͑Δ

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·ͣॻ͔ͳ͍

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v.is_a?(TrueClass)

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v == true

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2. Rubyʹ BooleanΫϥε͕ ͳͯ͘΋Α͍ཧ༝

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https://bugs.ruby- lang.org/issues/ 12515

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Create "Boolean" superclass of TrueClass / FalseClass

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ɹɹɹɹɹɹɹ٫Լ Status: Rejected

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Rejected for several reasons: many gems and libraries had already introduced Boolean class. I don't want to break them. true and false are the only representative of true-false values. In Ruby. nil and false are falsy values, and everything else is a true value. There's no meaning for having a superclass of TrueClass and FalseClass as Boolean. Matz. ʢԼઢ͸Ҿ༻ऀʣ

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Rubyʹ͓͍ͯ͸ trueͱfalse͸ ਅِ஋ͷ୅ද

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ਅͷ୅දɿtrue ِͷ୅දɿfalse

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ͦΕҎ֎ͷɺ ਅͷྫɿ42, [], … ِͷྫɿnil

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trueͱfalse͸ 1Ϗοτͷ৘ใྔ

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trueͱfalse͸ Կ΋ڞ༗ ͍ͯ͠ͳ͍

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trueͱfalse͕ ಉ͡Ϋϥεʹ ଐ͢Δͱ͸ʁ

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Ϋϥεͱ͸ʁ

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ڞ௨͢Δ΋ͷ͕ ·ͱ·͍ͬͯΔ

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ଐ͍ͯ͠Δ Πϯελϯε͕ ଐੑΛڞ༗͠ͳ͍ʁ

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BooleanΫϥεʹ ϝιου͕ଘࡏ ͠ͳ͍ʁ

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ڞ௨ͷ਌Ϋϥε ʹ͸ҙຯ͕ͳ͍

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Ͱ΋Boolean͕ ͋ͬͨ΄͏͕ ศརͳͷͰ͸ʁ

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https://bugs.ruby- lang.org/issues/ 12515

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Ϣʔεέʔε

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v.is_a?(Boolean)

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ಉ͡ػೳɿ v == true || v == false

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΄΅͜Ε͚ͩ

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Θ͟Θ͟ޓ׵ੑΛ ؾʹͯ͠·Ͱ௥Ճ ͠ͳͯ͘Α͍

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RubyʹBoolean Ϋϥε͕ͳͯ͘΋ Α͍ཧ༝·ͱΊ

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RubyʹBooleanΫϥε͕ͳͯ͘΋Α͍ཧ༝ • trueͱfalse͕ڞ༗͢Δ΋ͷ͕Կ΋ͳ͍ • ڞ௨ͷ਌ΫϥεΛ࣋ͭ͜ͱʹҙຯ͕ͳ͍ • Ϣʔεέʔε͕গͳ͍ • ͦ͏·Ͱͯ͠࡞Δ΄ͲͰ͸ͳ͍ • ྺ࢙తཧ༝΋͋Γͦ͏ • طଘͷBooleanΫϥεΛഁյͯ͠͠·͏

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ࠓճͷൃදͰ ࢲֶ͕Μͩ͜ͱ

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ࠓճͷֶͼ • ҰͭͷissueΛਂ۷Δͱ৭ʑͳҙݟ͕ަΘ͞Ε͍ͯͯ໘ന͍ • ʮࣗવʯʮศརʯ͸ܾఆతͳཧ༝ʹͳΒͳ͍ͱ͖͕͋Δ • ࣮͸ଞͷݴޠʹ͸͍͍ͩͨBoolean͕͋Δ • ϓϩάϥϛϯάݴޠͷઃܭͰࣗ໌ͳ͜ͱ͸গͳ͍ʢͱࢥͬͨʣ

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Thank you!