kontlang-shift-reset-lisp

「Kontlang - shift/resetのあるLisp あるいはインタプリタを継続渡しスタイルで書くと何が嬉しいのか」
限定継続を扱えるようにする言語機能shift/resetを持つLispインタプリタを実装した話。
インタプリタを継続渡しスタイルとdefunctionalizationを使って書くことで継続をより簡単に制御することができた。

Transcript

1. ,POUMBOH
   TIJGUSFTFUͷ͋Δ-JTQ
   ͋Δ͍͸
   ΠϯλϓϦλΛܧଓ౉͠ελΠϧͰॻ͘ͱԿ͕خ͍͠ͷ͔ ![FIOQBBSE
   
2. w ϓϩάϥϚ
   w -JTQྺ̐೥
   w ͍ΖΜͳݴޠΛ৮ͬͨΓ࡞ͬͨΓ͢Δͷ͕޷͖
   w ࠷ۙ͸झຯͰ0$BNMΛ࢖͏͜ͱ͕ଟ͍
   w ͋ͻΔ͏͗͞͞ΜνʔϜʢޙظϰΟτήϯγϡλΠϯ೿ʣ
   w ϒϩάɿ
   [FIOQBBSEIBUFOBCMPHDPN
   w (JU)VC
   IUUQTHJUIVCDPN[FIOQBBSE ࣗݾ঺հ
3. ຊ೔ͷ࿩୊ w TIJGUSFTFU
   ϓϩάϥϛϯάʹೖ໳͍ͨ͠
   w ͦͷͨΊʹTIJGUSFTFUͷ͋ΔݴޠΛ࣮૷͍ͨ͠
   w ܧଓ౉͠ελΠϧͰΠϯλϓϦλॻ͍ͯΈͨ
   w ͍Ζ͍Ζ໘ന͍͜ͱ͕͋ͬͨ
4. ݶఆܧଓͱ͸ʁߏ଄΍ࣗ࡞ํ๏ɺ Φεεϝͷݶఆܧଓͷ࢖͍ํΛղ આʂܧଓ΍Ϟφυͱͷҧ͍ͱ͸ʁ
5. ݶఆܧଓ http://pllab.is.ocha.ac.jp/~asai/cw2011tutorial/main-j.pdf
6. ܧଓ w ʮ͋ΔܭࢉΛ࣮ߦͨͦ͠ͷޙΛද͢΋ͷʯ
   w ʮ͜Ε͔ΒߦΘΕΔͰ͋Ζ͏ܭࢉΛύοέʔδԽͨ͠΋ ͷʯ
   w ʮϓϩάϥϜͷ
   جຊతʹ͸τοϓϨϕϧʹ໭Δ·Ͱͷ
   ࢒Γͷॲཧʯ ʮϞφυΛͭ͘Ζ͏ʯɹ!EJDP@MFRVFࢯ ʮͳΜͰ΋ܧଓʯɹ!BOPIBOBࢯ ʮ4DIFNFͱܧଓʯɹ!IBUTVHBJࢯ ϓϩάϥϛϯάͷੈքͷ֓೦ʹ͸ɺષͷެҊͷΑ͏ͳ΋ͷ͕͋Δɻ ͦΕΛઆ໌͢Δจষ͸΄ΜͷҰจͳͷʹɺ࠷ॳʹ໨ ʹ͢Δ࣌ɺ ͦͷจ͸શ͘ҙຯΛͳ͞ͳ͍ɺ҉߸ͷΑ͏ʹײ͡ΒΕΔɻ ͕ͩͻͱͨͼͦͷ֓೦Λཧղ͢Δͱɺ ͦͷ֓೦ ͷઆ໌͸͔֬ʹͦͷҰจͰઆ໌͞Ε͍ͯΔͷ͕Θ͔ΔͷͩɻɹʮͳΜͰ΋ܧଓʯɹ@anohanaࢯ https://www.slideshare.net/dico_leque/ss-14149810 http://practical-scheme.net/docs/cont-j.html http://lqtmirage.hatenablog.com/entry/2017/05/23/101744
7. ܧଓ (+ 1 2 (* 3 4) (+ 5 6)) ྫ͑͹͜Μͳ͕ࣜ͋Δͱͯ͠
8. ܧଓ (+ 1 2 (* 3 4) (+ 5 6)) ͜ͷ෦෼ࣜͷධՁΛߟ͑Δͱ
9. ܧଓ (+ 1 2 X (+ 5 6))) (fn [X] ͦͷपғʹ͋Δ࢒Γͷ͕ࣜͦͷ ෦෼ࣜͷʮܧଓʯͱͳΔɻ
   ͜ͷΑ͏ͳؔ਺Ͱ
   
    ͷܧଓ ͕දݱͰ͖Δ
10. ܧଓͱݶఆܧଓ w ޡɿʮݶఆܧଓʯ͸ʮܧଓʯػೳΛݶఆͯ͠࢖͍΍͘͢͠ ͨɾ࣮૷͠΍ͨ͘͢͠΋ͷͰ͋Δ
    w ਖ਼ɿʮݶఆܧଓʯ͸ัଊ͢ΔܧଓͷൣғΛҙਤతʹݶఆ͢ Δػೳ͕௥Ճ͞Ε͍ͯΔɻදݱྗ͸ݶఆܧଓͷํ্͕
11. ݶఆܧଓͱϞφυ https://dl.acm.org/doi/pdf/10.1145/174675.178047 http://okmij.org/ftp/continuations/against-callcc.html
12. ໰୊఺ w TIJGUSFTFU
    ϓϩάϥϛϯάೖ໳͸0DIB$BNMΛ࢖͍ͬͯΔ
    w 0$BNMϕʔεͰTIJGUSFTFU͕ೖͬͨಠࣗݴޠ
    w νϡʔτϦΞϧΛ΍ΔͨΊ͚ͩʹॲཧܥΠϯετʔϧ͢Δ ͷ΋ͳ͊ɾɾɾ
    w ΋ͬͱ௚઀ʮܧଓʯʹ৮ΕͯΈ͍ͨʂ
13. ͦ͏ͩɺΠϯλϓϦλࣗ࡞͠Α͏
14. λωຊ w ΠϯλϓϦλ࣮૷Λ௨ͯ͡ϓϩ άϥϛϯάݴޠͷॾ֓೦ΛֶͿ ͨΊͷຊ
    w ͍ΖΜͳػೳΛஈ֊తʹ௥Ճ
    w ୈষɺୈষ͕ܧଓͷ࿩
    w ୈষ͕۩ମతʹΠϯλϓϦλ Λܧଓ౉͠Ͱॻ͖ͳ͓͢ํ๏
15. &P1-ྱࢍ w ࠓճͷτϐοΫҎ֎ʹ΋ωλຬࡌ
    w ϛϡʔλϒϧͳม਺ɾλϓϧ
    w ܕਪ࿦
    w .-Ϟδϡʔϧ΍ϑΝϯΫλʔ
    w ΦϒδΣΫτ
    w ྫ֎ɺεϨουɺ$BMMCZ/BNF
    ʜ
16. &P1-ͷݴޠબ୒ ϗετݴޠɿ3BDLFU ιʔεݴޠɿ.-ͬΆ͍ let rec even x = if zero?(x) then 1 else (odd -(x,1)) and odd x = if zero?(x) then 0 else (even -(x,1)) in odd 13 (define value-of (exp env) (cases expression exp (const-exp (num) (num-val num)) (var-exp (var) (apply-env env var)) (diff-exp (exp1 exp2) (let ((val1 (value-of exp1 env)) (val2 (value-of exp2 env))) (let ((num1 (expval->num val1)) (num2 (expval->num val2))) (num-val (- num1 num2))))) ...))
17. ,POUMBOHͷݴޠબ୒ ϗετݴޠɿ0$BNM let rec eval env e = match e with | Exp.Int n -> Val.Int n | Exp.Var s -> Env.find env s | Exp.Call(e1, e2) -> let v1 = eval env e1 in let v2 = eval env e2 in call v1 v2 ... ιʔεݴޠɿ$MPKVSFͬΆ͍ (letfn [double [x] (* x 2)] (letrec [map [f xs] (if (nil? xs) nil (cons (f (car xs)) (map f (cdr xs))))] (map double (list 1 2 3 4 5))))
18. 0$BNMͷར఺ w ͔͕ͬ͜গͳ͍ʢӕͰ͢ɺ෺Λ౤͛ͳ͍Ͱʣ
    w ୅਺తσʔλܕͱύλʔϯϚον
    w ڧྗͳύʔαδΣωϨʔλ.FOIJS
    w ͋Β͔ͨؔ਺ܕɺ࣌ʑ෭࡞༻
19. -JTQจ๏ͷར఺ w ύʔαॻ͘ͷָ͕ʂ
    w จ๏΄΅ߟ͑ͳ͍͍ͯ͘
    w ϚΫϩʁ
20. ,POUMBOHͱ͸ʁߏ଄΍ࣗ࡞ํ๏ɺΦ εεϝͷΠϯλϓϦλͷબͼํΛղ આʂ4DIFNF΍$MPKVSFͱͷҧ͍ͱ͸ʁ
21. ,POUMBOH
22. ,POUMBOH঺հ w $MPKVSFͬΆ͍ʢʁʣจ๏
    w ΄΅७ਮؔ਺ܕ
    w ஋͸Πϛϡʔλϒϧ
    w ϝϞϦʹରͯ͠มߋΛՃ͑Δํ๏͸ͳ͍
    w QSJOU΍SFBE͸͋Δ
    w ϚΫϩ
    w ݶఆܧଓ
23. ίʔυαϯϓϧ (letfn [double [x] (* x 2)] (letrec [map [f xs] (if (nil? xs) nil (cons (f (car xs)) (map f (cdr xs))))] (map double (list 1 2 3 4 5))))
24. ϚΫϩ w ශऑͳ͕Βஔ׵ϕʔεͷୈҰڃϚΫϩ
    w ΫϩʔδϟΛ࣋ͨͳ͍ͷͰμΠφϛοΫɾείʔϓ
    w ϨΩγΧϧɾείʔϓʹ͢Δ৔߹ɺஔ׵͢ΔલʹҾ਺Λ UIVOL͢Ε͹͍͍ʁ
    w ʮϞφυΛͭ͘Ζ͏ʯͷSFJGZΛ࣮૷͍ͨ͠ (let [m (macro [x y] (do [y x]))] (m (println "hello") (println "goodbye")))
25. ͪΐͬͱσϞ EVOF
    FYFD
    NBJOFYF
26. ࣮૷ղઆ w ࣜͱ஋
    w ܧଓ౉͠ελΠϧ
    w εςοϓ࣮ߦ
    w ຤ඌݺͼग़͠࠷దԽ
27. ࣜͱ஋
28. ࣜͱ஋ w ͳΜͪΌͬͯ4ࣜ
    w ࣜͱ஋͸ผ෺
    w ࣜΛධՁͯ͠஋ʹ͢Δ
    w ΞτϜͱϦετͰ͸ͳ͘"45͕͋Δ
    w ΋ͱ΋ͱ.-ͬΆ͍ݴޠʹ-JTQจ๏Λඃ͍ͤͯΔͷͰɾɾɾ
29. ࣜͱ஋ module Env = struct type t = (string * Val.t) list let rec find env s = match env with | [] -> failwith "Not found" | (s',v)::env' -> if s = s' then v else find env' s end let rec eval env e = match e with | Exp.Int n -> Val.Int n | Exp.Var s -> Env.find env s | Exp.Call(e1, e2) -> let v1 = eval env e1 in let v2 = eval env e2 in call v1 v2 module Exp = struct type t = | Int of int | Var of string | Call of t * t end module Val = struct type t = | Int of int | Op of string * (Val.t -> Val.t) end
30. ܧଓ౉͠ελΠϧ
31. ී௨ͷΠϯλϓϦλ let rec eval env e = match e with | Exp.Int n -> Val.Int n | Exp.Var s -> Env.find env s | Exp.Call(e1, e2) -> let v1 = eval env e1 in let v2 = eval env e2 in call v1 v2
32. ܧଓ౉͠ελΠϧ let rec eval env cont e = match e with | Exp.Int n -> cont (Val.Int n) | Exp.Var s -> cont (Env.find env s) | Exp.Call(e1, e2) -> let cont’ v = let cont’’ w = cont (call v w) in eval env cont’’ e2 in eval env cont’ e1
33. %FGVODUJPOBMJ[BUJPO let rec eval env cont e = match e with | Exp.Int n -> apply_cont env cont (Val.Int n) | Exp.Var s -> apply_cont env cont (Env.find env s) | Exp.Call(e1, e2) -> eval env (Cont.Call1(e2)::cont) e1 and apply_cont env cont v = match cont with | [] -> v | Cont.Call1(e)::cont' -> eval env (Cont.Call2(v)::cont') e | Cont.Call2(v')::cont' -> apply_cont env cont' (call v' v) module Cont = struct type t' = | Call1 of Exp.t | Call2 of Val.t type t = t' list end
34. τϥϯϙϦϯԽ let eval env cont e = match e with | Exp.Int n -> Res.ApplyCont(env, cont, Val.Int n) | Exp.Var s -> Res.ApplyCont(env, cont, Env.find env s) | Exp.Call(e1, e2) -> Res.Eval(env, Cont.Call1(e2)::cont, e1) let apply_cont env cont v = match cont with | [] -> Res.Done v | Cont.Call1(e)::cont' -> Res.Eval(env, Cont.Call2(v)::cont', e) | Cont.Call2(v')::cont' -> Res.ApplyCont(env, cont', call v' v) let rec trampoline r = match r with | Res.Done v -> v | Res.Eval(env, cont, e) -> trampoline (eval env cont e) | Res.ApplyCont(env, cont, v) -> trampoline (apply_cont env cont v) module Res = struct type t = | Done of Val.t | Eval of Env.t * Cont.t * Exp.t | ApplyCont of Env.t * Cont.t * Val.t end
35. εςοϓ࣮ߦ ௨ৗͷΠϯλϓϦλͱ͸ผʹɺεςοϓ͝ͱʹΠϯλϓϦλ ͷঢ়ଶΛදࣔ͢ΔTUFQXJTFΠϯλϓϦλ͕͋Δ let rec trampoline’ r = match r with | Res.Done v -> v | Res.Eval(env, cont, e) -> pause_and_display r; trampoline (eval env cont e) | Res.ApplyCont(env, cont, v) -> pause_and_display r; trampoline (apply_cont env cont v)
36. ͪΐͬͱσϞ EVOF
    FYFD
    TUFQXJTFFYF
37. ຤ඌݺͼग़͠࠷దԽ ຤ඌ࠶ؼ (letrec [f [acc xs] (if (nil? xs) acc (f (+ acc (car xs)) (cdr xs)))] (f 0 (list 1 2 3))) ඇ຤ඌ࠶ؼ (letrec [f [xs] (if (nil? xs) 0 (+ (car xs) (f (cdr xs))))] (f (list 1 2 3))) w φΠʔϒͳ࣮૷ͩͱ຤ඌ࠶ؼͰ΋࠶ ؼ͢Δ͝ͱʹܧଓελοΫɺม਺ε λοΫͱ΋ʹੵΈ্͕ͬͯ͠·͏
    w ؔ਺͕຤ඌݺͼग़͠ͷܗʹͳͬͯ ͍Δ৔߹ɺؔ਺ద༻ͷ࣌఺Ͱܧଓ ελοΫͷઌ಄ʹ$POU&OW͕ࡌͬ ͍ͯΔɻͦΕʹରԠ͢Δม਺؀ڥ ͱͱ΋ʹελοΫ͔Β֎ͯ͠΍Δͩ ͚Ͱ຤ඌݺͼग़͠࠷దԽ͕࣮૷Ͱ ͖Δ
38. ΋͏ҰճσϞ EVOF
    FYFD
    TUFQXJTFFYF
39. ຤ඌݺͼग़͠࠷దԽ w ߦ௥ՃͰ຤ඌݺͼग़͠࠷దԽ͕࣮૷Ͱ͖ͨ
40. ͋Εɺݶఆܧଓ͸ʁ
41. ࠓޙͷ՝୊ w ݶఆܧଓΛ࣮૷͍ͨ͠ɾɾɾ
    w Πϝʔδ͸͋Δɻ͋ͱͪΐͬͱʢόά͍ͬͯΔʣ
    w Ϋϩʔδϟ͕େม
    w ؔ਺ͷ෦෼ద༻
    w εςοϓ࣮ߦΛਐԽ
    w 6*ͷ޲্
    w Τϥʔ࣌ʹఀࢭɺר͖໭͠ɺࣜΛҰ෦มߋ
42. ݴ͍͍ͨ͜ͱ w &P1-͸͍͍ͧ
    w ܧଓ౉͠ελΠϧ͸͍͍ͧ
    w EFGVODUJPOBMJ[BUJPO͸͍͍ͧ
    w ͪͳΈʹࠓճͷ͜Εɺ$&,ػցͱ͍͏ந৅ػցͱ΄΅ಉ Ұͷ΋ͷͷΑ͏ͩʢࢿྉ࡞੒தʹ஌ͬͨʣ
    w ఏএऀ͸'FMMFJTFOͱ'MBUUͷ໛༷ɻ΍ͬͺΓ-JTQ͔
43. ଓ͖͸ϒϩάͰ https://zehnpaard.hatenablog.com