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,POUMBOH
TIJGUSFTFUͷ͋Δ-JTQ
͋Δ͍
ΠϯλϓϦλΛܧଓ͠ελΠϧͰॻ͘ͱԿ͕خ͍͠ͷ͔
![FIOQBBSE
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w ϓϩάϥϚ
w -JTQྺ̐
w ͍ΖΜͳݴޠΛ৮ͬͨΓ࡞ͬͨΓ͢Δͷ͕͖
w ࠷ۙझຯͰ0$BNMΛ͏͜ͱ͕ଟ͍
w ͋ͻΔ͏͗͞͞ΜνʔϜʢޙظϰΟτήϯγϡλΠϯʣ
w ϒϩάɿ[FIOQBBSEIBUFOBCMPHDPN
w (JU)VCIUUQTHJUIVCDPN[FIOQBBSE
ࣗݾհ
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ຊͷ
w TIJGUSFTFUϓϩάϥϛϯάʹೖ͍ͨ͠
w ͦͷͨΊʹTIJGUSFTFUͷ͋ΔݴޠΛ࣮͍ͨ͠
w ܧଓ͠ελΠϧͰΠϯλϓϦλॻ͍ͯΈͨ
w ͍Ζ͍Ζ໘ന͍͜ͱ͕͋ͬͨ
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ݶఆܧଓͱʁߏࣗ࡞ํ๏ɺ
Φεεϝͷݶఆܧଓͷ͍ํΛղ
આʂܧଓϞφυͱͷҧ͍ͱʁ
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ݶఆܧଓ
http://pllab.is.ocha.ac.jp/~asai/cw2011tutorial/main-j.pdf
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ܧଓ
w ʮ͋ΔܭࢉΛ࣮ߦͨͦ͠ͷޙΛද͢ͷʯ
w ʮ͜Ε͔ΒߦΘΕΔͰ͋Ζ͏ܭࢉΛύοέʔδԽͨ͠
ͷʯ
w ʮϓϩάϥϜͷ جຊతʹτοϓϨϕϧʹΔ·Ͱͷ
Γͷॲཧʯ
ʮϞφυΛͭ͘Ζ͏ʯɹ!EJDP@MFRVFࢯ
ʮͳΜͰܧଓʯɹ!BOPIBOBࢯ
ʮ4DIFNFͱܧଓʯɹ!IBUTVHBJࢯ
ϓϩάϥϛϯάͷੈքͷ֓೦ʹɺષͷެҊͷΑ͏ͳͷ͕͋Δɻ ͦΕΛઆ໌͢Δจষ΄ΜͷҰจͳͷʹɺ࠷ॳʹ
ʹ͢Δ࣌ɺ ͦͷจશ͘ҙຯΛͳ͞ͳ͍ɺ҉߸ͷΑ͏ʹײ͡ΒΕΔɻ ͕ͩͻͱͨͼͦͷ֓೦Λཧղ͢Δͱɺ ͦͷ֓೦
ͷઆ໌͔֬ʹͦͷҰจͰઆ໌͞Ε͍ͯΔͷ͕Θ͔ΔͷͩɻɹʮͳΜͰܧଓʯɹ@anohanaࢯ
https://www.slideshare.net/dico_leque/ss-14149810
http://practical-scheme.net/docs/cont-j.html
http://lqtmirage.hatenablog.com/entry/2017/05/23/101744
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ܧଓ
(+ 1
2
(* 3 4)
(+ 5 6))
ྫ͑͜Μͳ͕ࣜ͋Δͱͯ͠
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ܧଓ
(+ 1
2
(* 3 4)
(+ 5 6))
͜ͷ෦ࣜͷධՁΛߟ͑Δͱ
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ܧଓ
(+ 1
2
X
(+ 5 6)))
(fn [X] ͦͷपғʹ͋ΔΓͷ͕ࣜͦͷ
෦ࣜͷʮܧଓʯͱͳΔɻ
͜ͷΑ͏ͳؔͰ
ͷܧଓ
͕දݱͰ͖Δ
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ܧଓͱݶఆܧଓ
w ޡɿʮݶఆܧଓʯʮܧଓʯػೳΛݶఆ͍ͯ͘͢͠͠
ͨɾ࣮ͨ͘͢͠͠ͷͰ͋Δ
w ਖ਼ɿʮݶఆܧଓʯัଊ͢ΔܧଓͷൣғΛҙਤతʹݶఆ͢
Δػೳ͕Ճ͞Ε͍ͯΔɻදݱྗݶఆܧଓͷํ্͕
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ݶఆܧଓͱϞφυ
https://dl.acm.org/doi/pdf/10.1145/174675.178047
http://okmij.org/ftp/continuations/against-callcc.html
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w TIJGUSFTFUϓϩάϥϛϯάೖ0DIB$BNMΛ͍ͬͯΔ
w 0$BNMϕʔεͰTIJGUSFTFU͕ೖͬͨಠࣗݴޠ
w νϡʔτϦΞϧΛΔͨΊ͚ͩʹॲཧܥΠϯετʔϧ͢Δ
ͷͳ͊ɾɾɾ
w ͬͱʮܧଓʯʹ৮ΕͯΈ͍ͨʂ
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ͦ͏ͩɺΠϯλϓϦλࣗ࡞͠Α͏
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λωຊ
w ΠϯλϓϦλ࣮Λ௨ͯ͡ϓϩ
άϥϛϯάݴޠͷॾ֓೦ΛֶͿ
ͨΊͷຊ
w ͍ΖΜͳػೳΛஈ֊తʹՃ
w ୈষɺୈষ͕ܧଓͷ
w ୈষ͕۩ମతʹΠϯλϓϦλ
Λܧଓ͠Ͱॻ͖ͳ͓͢ํ๏
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&P1-ྱࢍ
w ࠓճͷτϐοΫҎ֎ʹωλຬࡌ
w ϛϡʔλϒϧͳมɾλϓϧ
w ܕਪ
w .-ϞδϡʔϧϑΝϯΫλʔ
w ΦϒδΣΫτ
w ྫ֎ɺεϨουɺ$BMMCZ/BNFʜ
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&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)))))
...))
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,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))))
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0$BNMͷར
w ͔͕ͬ͜গͳ͍ʢӕͰ͢ɺΛ͛ͳ͍Ͱʣ
w తσʔλܕͱύλʔϯϚον
w ڧྗͳύʔαδΣωϨʔλ.FOIJS
w ͋Β͔ͨؔܕɺ࣌ʑ෭࡞༻
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-JTQจ๏ͷར
w ύʔαॻ͘ͷָ͕ʂ
w จ๏΄΅ߟ͑ͳ͍͍ͯ͘
w ϚΫϩʁ
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,POUMBOHͱʁߏࣗ࡞ํ๏ɺΦ
εεϝͷΠϯλϓϦλͷબͼํΛղ
આʂ4DIFNF$MPKVSFͱͷҧ͍ͱʁ
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,POUMBOH
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,POUMBOHհ
w $MPKVSFͬΆ͍ʢʁʣจ๏
w ΄΅७ਮؔܕ
w Πϛϡʔλϒϧ
w ϝϞϦʹରͯ͠มߋΛՃ͑Δํ๏ͳ͍
w QSJOUSFBE͋Δ
w ϚΫϩ
w ݶఆܧଓ
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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))))
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ϚΫϩ
w ශऑͳ͕ΒஔϕʔεͷୈҰڃϚΫϩ
w ΫϩʔδϟΛ࣋ͨͳ͍ͷͰμΠφϛοΫɾείʔϓ
w ϨΩγΧϧɾείʔϓʹ͢Δ߹ɺஔ͢ΔલʹҾΛ
UIVOL͢Ε͍͍ʁ
w ʮϞφυΛͭ͘Ζ͏ʯͷSFJGZΛ࣮͍ͨ͠
(let [m (macro [x y] (do [y x]))]
(m (println "hello") (println "goodbye")))
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ͪΐͬͱσϞ
EVOFFYFDNBJOFYF
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࣮ղઆ
w ࣜͱ
w ܧଓ͠ελΠϧ
w εςοϓ࣮ߦ
w ඌݺͼग़͠࠷దԽ
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ࣜͱ
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ࣜͱ
w ͳΜͪΌͬͯ4ࣜ
w ࣜͱผ
w ࣜΛධՁͯ͠ʹ͢Δ
w ΞτϜͱϦετͰͳ͘"45͕͋Δ
w ͱͱ.-ͬΆ͍ݴޠʹ-JTQจ๏Λඃ͍ͤͯΔͷͰɾɾɾ
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ࣜ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
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ܧଓ͠ελΠϧ
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ී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
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ܧଓ͠ελΠϧ
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
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%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
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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
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εςοϓ࣮ߦ
௨ৗͷΠϯλϓϦλͱผʹɺεςοϓ͝ͱʹΠϯλϓϦλ
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)
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ͪΐͬͱσϞ
EVOFFYFDTUFQXJTFFYF
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ඌݺͼग़͠࠷దԽ
ඌ࠶ؼ
(letrec [f [acc xs]
(if (nil? xs)
acc
(f (+ acc (car xs)) (cdr xs)))]
(f 0 (list 1 2 3)))
ඇඌ࠶ؼ
(letrec [f [xs]
(if (nil? xs)
0
(+ (car xs) (f (cdr xs))))]
(f (list 1 2 3)))
w φΠʔϒͳ࣮ͩͱඌ࠶ؼͰ࠶
ؼ͢Δ͝ͱʹܧଓελοΫɺมε
λοΫͱʹੵΈ্͕ͬͯ͠·͏
w ͕ؔඌݺͼग़͠ͷܗʹͳͬͯ
͍Δ߹ɺؔద༻ͷ࣌Ͱܧଓ
ελοΫͷઌ಄ʹ$POU&OW͕ࡌͬ
͍ͯΔɻͦΕʹରԠ͢Δมڥ
ͱͱʹελοΫ͔Β֎ͯ͠Δͩ
͚Ͱඌݺͼग़͠࠷దԽ͕࣮Ͱ
͖Δ
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͏ҰճσϞ
EVOFFYFDTUFQXJTFFYF
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ඌݺͼग़͠࠷దԽ
w ߦՃͰඌݺͼग़͠࠷దԽ͕࣮Ͱ͖ͨ
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͋Εɺݶఆܧଓʁ
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ࠓޙͷ՝
w ݶఆܧଓΛ࣮͍ͨ͠ɾɾɾ
w Πϝʔδ͋Δɻ͋ͱͪΐͬͱʢόά͍ͬͯΔʣ
w Ϋϩʔδϟ͕େม
w ؔͷ෦ద༻
w εςοϓ࣮ߦΛਐԽ
w 6*ͷ্
w Τϥʔ࣌ʹఀࢭɺר͖͠ɺࣜΛҰ෦มߋ
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ݴ͍͍ͨ͜ͱ
w &P1-͍͍ͧ
w ܧଓ͠ελΠϧ͍͍ͧ
w EFGVODUJPOBMJ[BUJPO͍͍ͧ
w ͪͳΈʹࠓճͷ͜Εɺ$&,ػցͱ͍͏நػցͱ΄΅ಉ
ҰͷͷͷΑ͏ͩʢࢿྉ࡞தʹͬͨʣ
w ఏএऀ'FMMFJTFOͱ'MBUUͷ༷ɻͬͺΓ-JTQ͔
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ଓ͖ϒϩάͰ
https://zehnpaard.hatenablog.com