Curry: An Integrated Functional Logic Language

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:eval f Show the definitional tree (see Section D.1) of function f. :quit Exit the system. 37
A Example Programs This section contains a few example programs together with some initial expressions and their computed results. A.1 Operations on Lists Here are simple operations on lists. Note that, due to the logic programming features of <strong>Curry</strong>, append can be used to split lists. We exploit this property to define the last element of a list in a very simple way. -- Concatenation of two lists: append :: [t] -> [t] -> [t] append [] ys = ys append (x:xs) ys = x:append xs ys -- Naive reverse of all list elements: rev :: [t] -> [t] rev [] = [] rev (x:xs) = append (rev xs) [x] -- Last element of a list: last :: [t] -> t last xs | append _ [x] =:= xs = x where x free Expressions and their evaluated results: append [0,1] [2,3] ❀ [0,1,2,3] append L M =:= [0,1] ❀ {L=[],M=[0,1]} | {L=[0],M=[1]} | {L=[0,1],M=[]} rev [0,1,2,3] ❀ [3,2,1,0] last (append [1,2] [3,4]) ❀ 4 38
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: 10 Literate Programming To encourag
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 and 58: putStr [] = done putStr (c:cs) = pu
Page 59 and 60: owseList (g:gs) = browse g >> putCh
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_

Curry: An Integrated Functional Logic Language

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