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Regular expressions basics/正規表現の基本
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Kishikawa Katsumi
July 26, 2022
Programming
7
800
Regular expressions basics/正規表現の基本
Regular expressions basics/正規表現の基本
Kishikawa Katsumi
July 26, 2022
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Transcript
ਖ਼نදݱͷجຊ Regular expressions basics
Swift Regex
https://swiftregex.com/
ਖ਼نදݱͱ • จࣈྻͷू߹ʢύλʔϯʣΛද͢൚༻తͳه๏ • [bc]ookbook·ͨcookʹϚον͢Δ
Ϧςϥϧ Literal Characters • a • Jack is a boy,
• cat • About cats and dogs
ϝλจࣈ Special Characters (Meta Characters) • ಛผͳҙຯΛ࣋ͭ12ͷจࣈʢϦςϥϧͱͯ͠ѻ͏ʹΤεέʔϓ͕ඞཁɻʢྫʣ1\+1=2ʣ • όοΫεϥογϡ \
• ΩϟϨοτ ^ • υϧϚʔΫ $ • υοτʢϐϦΦυʣ . • ύΠϓ | • ΫΤενϣϯϚʔΫ ? • ΞελϦεΫ * • ϓϥε + • ։ؙ͖Χοί ( • ดؙ͡Χοί ) • ։͖֯Χοί [ • ։͖Χοί {
੍ޚจࣈ Non-Printable Characters (Control Characters, Escape sequence) • \t •
λϒʹϚον͢Δ • \n • վߦʹϚον͢Δ
จࣈΫϥε Character Classes (Character Sets) • ෳͷจࣈͷத͔Β̍ͭͷจࣈʹϚον͢Δ • a·ͨeʹϚονͤ͞Δʹ[ae]ͱॻ͘ •
ʢྫʣgr[ae]y • gray·ͨgreyʹϚον • จࣈΫϥε1ͭͷจࣈʹϚον͢Δ • Χοίͷதͷจࣈͷॱংؔͳ͍
จࣈΫϥε Character Classes (Character Sets) • จࣈΫϥεͷதͰϋΠϑϯΛ༻ͯ͠ൣғΛࢦఆͰ͖Δ • [0-9] •
͔̌Β̕ͷؒͷܻ̍ͷࣈʹϚον • [0-9a-fA-F] • େจࣈͱখจࣈΛ۠ผͤͣʹɺ16ਐͷࣈܻ̍ʹϚον • ൱ఆจࣈΫϥεʢNegated Character Classesʣ • [^0-9\r\n] • ࣈ·ͨվߦͰͳ͍ҙͷจࣈʹϚον
จࣈΫϥεʢͷུه๏ʣ Shorthand Character Classes • จࣈΫϥεͷதͰΑ͘ΘΕΔͷΛ؆୯ʹॻ͚ΔΑ͏ʹ͋Β͔͡Ί༻ҙ͞Εͨه๏ • \d[0-9]ͷུه๏ • UnicodeΛαϙʔτ͢ΔڥͰࣈؙࣈͳͲͯ͢ͷࣈʹϚον
• \w “word character” [A-Za-z0-9_]ͱಉ͡ʢΞϯμʔείΞؚ͕·ΕΔ͜ͱʹҙʣ • UnicodeΛαϙʔτ͢ΔڥͰ͍Ζ͍ΖͳจࣈʹϚον • \s “whitespace character” ۭനจࣈʹϚον [ \t\r\n\f] • UnicodeΛαϙʔτ͢ΔڥͰUnicodeͷʮseparatorʯΧςΰϦͷͯ͢ͷจࣈʹϚον
υοτʢϐϦΦυʣ The Dot Matches (Almost) Any Character • վߦจࣈΛআ̍͘จࣈʹϚον •
“dot matches all”·ͨ“single line”Ϟʔυʢϓϩάϥϛϯάݴޠਖ਼نදݱΤ ϯδϯʹΑͬͯݺͼํҟͳΔʣΛࢦఆ͢ΔͱվߦจࣈΛؚΉҙͷ1จࣈʹ Ϛον • gr.yɺgrayɺgrayɺgr%yͳͲʹϚον • υοτڧྗʹͳΜͰϚον͢ΔͷͰ͍͗͢ͳ͍ • จࣈΫϥε൱ఆจࣈΫϥεΛΘΓʹ͏
ΞϯΧʔ Anchors • จࣈͰͳ͘ҐஔʹϚον • ^ • จࣈྻͷઌ಄ʹϚον • $
• จࣈྻͷඌʹϚον • ΄ͱΜͲͷਖ਼نදݱ“multi-line”Ϟʔυ͕͋Γɺ ^վߦͷޙΖɺ $վߦͷલʹϚον͢Δ • \b • ୯ޠڥքʹϚον • ୯ޠڥքͱ\wͰϚονͰ͖ΔจࣈͱɺͰ͖ͳ͍จࣈͷؒͷҐஔ
બ Alternation • ཧʢORʣ • cat|dog • About cats and
dogs • cat|dog|mouse| fi sh • ͖ͳ͚ͩͭͳ͛Δ͜ͱ͕Ͱ͖Δ • cat|dog food • cat·ͨdog foodʹϚον • cat food͔dog foodʹϚονͤ͞Δʹɺ(cat|dog) foodͷΑ͏ʹબΛάϧʔϓԽ͢Δ
܁Γฦ͠ Repetition • ΫΤενϣϯϚʔΫʮ?ʯ • Optional • colou?rcolor·ͨcolourʹϚον • ΞελϦεΫʮ*ʯ
• ̌ճҎ্ͷ܁Γฦ͠ • <[A-Za-z][A-Za-z0-9]*> • ଐੑ͕ͳ͍HTMLλάʹϚον • ϓϥεʮ+ʯ • ̍ճҎ্ͷ܁Γฦ͠ • Χοίʮ{n,m}ʯ • ࢦఆճͷ܁Γฦ͠ • \b[1-9][0-9]{3}b • 1000͔Β9999ͷࣈʹϚον • \b[1-9][0-9]{2,4}\b • 100͔Β99999ͷࣈʹϚον
άϧʔϓͱΩϟϓνϟ Grouping and Capturing • ΧοίͰғΉͱάϧʔϓԽ͞ΕΔ • άϧʔϓʹରͯ͠܁Γฦ͠ΛࢦఆͰ͖Δ • Set(Value)?
• Set·ͨSetValueʹϚον • ௨ৗͷؙΧοίΩϟϓνϟάϧʔϓΛ࡞͢Δ • Set(Value)?ͷਖ਼نදݱͰSetValue͕Ϛονͨ͠߹ɺάϧʔϓ̍ʹΞΫηε͢ΔͱValue͕औΓग़ͤΔ • Ωϟϓνϟ͕ඞཁͳ͍߹Set(?:Value)?ͱ͢ΔͱΩϟϓνϟ͠ͳ͍άϧʔϓ͕࡞Ͱ͖Δ • ؙΧοίͷޙͷΫΤενϣϯϚʔΫͱɺ̌ճҎ্ͷ܁Γฦ͠ͷࢦఆͷΫΤενϣϯϚʔΫΛࠞಉ͠ͳ͍Α͏ʹ ҙ
ޙํࢀর Backreferences • ΩϟϓνϟάϧʔϓͰΩϟϓνϟʢϚονʣͨ͠༰ʹϚον • ΩϟϓνϟάϧʔϓʹϚονͨ݁͠ՌΛ࠶ར༻Ͱ͖Δ • <([A-Z][A-Z0-9]*)\b[^>]*>.*?</\1> • HTMLλάʹϚονʢΩϟϓνϟάϧʔϓʹϚονͨ͠։࢝λάΛऴྃλάͰ
࠶ར༻͍ͯ͠Δʣ
໊લ͖άϧʔϓʢΩϟϓνϟʣͱޙํࢀর Named Groups and Backreferences • ΩϟϓνϟͷࢀরΛ൪߸Ͱཧ͢Δͷେมͩ͠ɺՃআͰͣΕΔͷͰ໊લΛ͚ΒΕΔ • ߏจʢ໊લ͖άϧʔϓʣ •
(?P<name>group) • ߏจʢޙํࢀরʣ • (?P=name) • <(?P<tag>[A-Z][A-Z0-9]*)\b[^>]*>.*?</(?P=tag)> • HTMLλάʹϚονʢ <([A-Z][A-Z0-9]*)\b[^>]*>.*?</\1>ͱಉ͡ʣ • ߏจʢ໊લ͖Ωϟϓνϟʢ.NETʣʣ • (?<name>group)·ͨ(?’name'group) • ߏจʢ໊લʹΑΔࢀরʢ.NETʣʣ • \k<name>·ͨ\k'name'
ઌಡΈͱޙಡΈ Lookaround (Lookahead/Lookback(Lookbehind)) • ಛघͳάϧʔϓͰɺΞϯΧʔͷΑ͏ʹϚονͨ݁͠ՌͷҐஔΛࢦఆ͢Δ • ʢྫʣ\d+(?=€) • ͷޙʹʮ€ʯ͕ଓ͘จࣈྻʹϚον •
1 turkey costs 30€ͷ30ʹϚον • ߏจʢߠఆઌಡΈʢPositive lookaheadʣʣ • X(?=Y) • ߏจʢ൱ఆઌಡΈʢNegative lookaheadʣʣ • X(?!Y) • ߏจʢߠఆޙಡΈʢPositive lookbehindʣʣ • (?<=Y)X • ߏจʢ൱ఆޙಡΈʢNegative lookbehindʣʣ • (?<!Y)X
References • Regular-Expressions.info https://www.regular-expressions.info/ • Swift Regex https://swiftregex.com/