Curry: An Integrated Functional Logic Language

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-- Encapsulated search -- primitive operator to control non-determinism try :: (a->Success) -> [a->Success] -- compute all solutions via depth-first search solveAll :: (a->Success) -> [a->Success] solveAll g = collect (try g) where collect [] = [] collect [g] = [g] collect (g1:g2:gs) = concat (map solveAll (g1:g2:gs)) -- compute first solution via depth-first search once :: (a->Success) -> (a->Success) once g = head (solveAll g) -- compute all values of solutions via depth-first search findall :: (a->Success) -> [a] findall g = map unpack (solveAll g) -- compute best solution via branch-and-bound with depth-first search best :: (a->Success) -> (a->a->Bool) -> [a->Success] -- try to find a solution to a search goal via a fair search -- (and fail if there is no solution) tryone :: (a->Success) -> a tryone eval choice tryone g | g x = x where x free -- compute one solution with a fair search strategy one :: (a->Success) -> [a->Success] one g = solveAll \x -> x =:= tryone g -- compute one solution with a fair search satisfying a condition condSearch :: (a->Success) -> (a->Bool) -> [a->Success] condSearch g cond = one \x -> g x & cond x =:= True -- show the solution of a solved constraint browse :: (a->Success) -> IO () browse g = putStr (show (unpack g)) -- show the solutions of a list of solved constraints browseList :: [a->Success] -> IO () browseList [] = done 57
owseList (g:gs) = browse g >> putChar ’\n’ >> browseList gs -- unpack a solution’s value from a (solved) search goal unpack :: (a -> Success) -> a unpack g | g x = x where x free 58
Page 1 and 2:
Curry An Integrated Functional Logi
Page 3 and 4:
9 Interface to External Functions a
Page 5 and 6:
and introduces a new n-ary type con
Page 7 and 8: tion 3 with σ(t1 . . . tn) = σ(t
Page 9 and 10: since the variables occurring in pa
Page 11 and 12: tified variable (and, thus, it can
Page 13 and 14: such cases, anonymous functions (λ
Page 15 and 16: ❀ {x=1,y=3} (The empty constraint
Page 17 and 18: 4.1.3 Functions The type t1 -> t2 i
Page 19 and 20: 4.1.8 Strings The type String is an
Page 21 and 22: g :: [a] -> [b] -> ([a],[b]) g x y
Page 23 and 24: In the last translation rule, conca
Page 25 and 26: to the module head. For instance, a
Page 27 and 28: module main where import m1 hiding
Page 29 and 30: take a character (string) and produ
Page 31 and 32: which takes a search goal and produ
Page 33 and 34: instance, if we want to compute the
Page 35 and 36: Intuitively, a function f declared
Page 37 and 38: 10 Literate Programming To encourag
Page 39 and 40: A Example Programs This section con
Page 41 and 42: A.3 Relational Programming Here is
Page 43 and 44: A.5 Constraint Solving and Concurre
Page 45 and 46: A.6 Concurrent Object-Oriented Prog
Page 47 and 48: B Standard Prelude This section con
Page 49 and 50: not :: Bool -> Bool not True = Fals
Page 51 and 52: foldr1 _ [x] = x foldr1 f (x1:x2:xs
Page 53 and 54: takeWhile _ [] = [] takeWhile p (x:
Page 55 and 56: enumFromThen n1 n2 = iterate ((n2-n
Page 57: putStr [] = done putStr (c:cs) = pu
Page 61 and 62: C.2 Layout Similarly to Haskell, a
Page 63 and 64: SimplePattern ::= VariableID | _ |
Page 65 and 66: D Operational Semantics of Curry Th
Page 67 and 68: Computation step for a single expre
Page 69 and 70: Eval [e; rule(l | c = r)] ⇒ {id
Page 71 and 72: to an expression): Eval [ϕ(e1, . .
Page 73 and 74: Eval [try(g)] ⇒ ⎧ [] if Eval [c
Page 75 and 76: D.8 Eliminating Local Declarations
Page 77 and 78: f ′′ x1 . . . xk y1 . . . ym =
Page 79 and 80: References [1] H. Aït-Kaci. An Ove
Page 81 and 82: [29] T. Johnsson. Lambda Lifting: T
Page 83 and 84: Index !!, 49 Dom, 64 VRan, 64 (), 1
Page 85 and 86: higher-order equation, 6 id, 46 if_
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Curry: An Integrated Functional Logic Language

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