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RecordDotSyntaxのあれこれ
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lotz
December 11, 2019
Programming
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RecordDotSyntaxのあれこれ
lotz
December 11, 2019
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Transcript
Record Dot Syntax ͷ͋Ε͜Ε By lotz 2019/12/11 ୈ2ճGHCษڧձ @ IIJ-II
RecordDotSyntax https://github.com/shayne-fletcher-da/ghc-proposals/blob/record-dot-syntax/proposals/0000-record-dot-syntax.md#motivation
RecordDotSyntaxͷجຊ https://github.com/shayne-fletcher-da/ghc-proposals/blob/record-dot-syntax/proposals/0000-record-dot-syntax.md#recorddotsyntax-language-extension
RecordDotSyntaxͷੜߏจ https://github.com/shayne-fletcher-da/ghc-proposals/blob/record-dot-syntax/proposals/0000-record-dot-syntax.md#recorddotsyntax-language-extension
Recordվળͷ্ʹ͋Δ ()$֦ு1SPQPTBM ()$7FSTJPO %VQMJDBUF3FDPSE'JFMET 0WFSMPBEFE-BCFMT 0WFSMPBEFE3FDPSE'JFMET "EETFU'JFMEUP)BT'JFME
/P'JFME4FMFDUPST "DDFQUFE 3FDPSE%PU4ZOUBY /&8
DAMLͰͷ࣮͋Γ • DAMLHaskell/ScalaͰ։ൃ͞Ε͍ͯΔɺ εϚʔτίϯτϥΫτهड़ݴޠ • DAMLͷ։ൃʹ͓͍ͯGHC Pluginsͱ͍͏ܗͰ RecordDotSyntaxͱ΄΅ಉ͡ػೳ͕ΘΕ͍ͯΔ
ఏҊͯ͠ΔͷDAMLͷਓ https://github.com/ghc-proposals/ghc-proposals/pull/282
PRͷԠ https://github.com/ghc-proposals/ghc-proposals/pull/282#issuecomment-540968106 *TUSPOHMZTVQQPSUUIFEJSFDUJPOPG USBWFMPGUIJTQSPQPTBM
PRͷԠ 5IFMPTTPGQPMZNPSQIJDVQEBUFJT BIVHFQSPCMFN JNP https://github.com/ghc-proposals/ghc-proposals/pull/282#issuecomment-541111003
PRͷԠ 5IJTQSPQPTBMJTGVMMPGVUUFSOPOTFOTF https://github.com/ghc-proposals/ghc-proposals/pull/282#issuecomment-541460439
> :t (.age) (.age) :: Person -> Int > :t
(. age) (. age) :: (Int -> c) -> Person -> c ۭനͷ༗Γແ͠Ͱ͜͜·Ͱҙຯ͕มΘΔͷ ॳ৺ऀʹ͘͠ͳ͍ʁ
ࠓͷεςʔλε https://github.com/ghc-proposals/ghc-proposals/pull/282#issuecomment-559259994 8JUIUIFUIDPNNFOU BGUFSSFBDUJPOTPOUIFJOJUJBM QPTU QBSUJDJQBOUTBOEBUMFBTUQPMMTPGVTFSTFOUJNFOU *EMJLFUPUVSOUIJTPWFSUPUIFDPNNJUUFF
ະղܾ https://twitter.com/ndm_haskell/status/1190680324495302658
͋Ε͜Ε
f a.b.c x ͷύʔε f a.foo.bar.baz.quux 12 f (a.foo.bar.baz.quux)
12 ͱධՁ͞ΕΔ ((f a).foo.bar.baz.quux) 12Ͱͳ͍ https://github.com/shayne-fletcher-da/ghc-proposals/blob/record-dot-syntax/proposals/0000-record-dot-syntax.md#record-selection
Lensʁ • f $ record ^. field ͕ f record.field
ͱॻ͚Δ • Lensෳࡶա͗Δ… • Lensͱ໊લۭ͕ؒҟͳΔͷͰҰॹʹ͑Δ https://github.com/shayne-fletcher-da/ghc-proposals/blob/record-dot-syntax/proposals/0000-record-dot-syntax.md#alternatives-to-this-proposal
͜͏͍͏දهແ͍ • ߋ৽ʹؔ͢Δߏจ • a{field * 2} • a{field <-
(*2)} • a{field * = 2} • ߋ৽ʹؔ͢ΔηΫγϣϯ • ({a=}) • ({a=b}) • (.lbl=) https://github.com/shayne-fletcher-da/ghc-proposals/blob/record-dot-syntax/proposals/0000-record-dot-syntax.md#alternatives-within-this-proposal
Ҏ্