50 lines
1.1 KiB
Haskell
50 lines
1.1 KiB
Haskell
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-- (c) MP-I (1998/9-2006/7) and CP (2005/6-2022/23)
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module NEList where
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import Cp
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-- (1) Datatype definition -----------------------------------------------------
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-- data [a] = a | (:) a ( a) deriving Show
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inl = either singl (uncurry (:))
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out [a] = Left a
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out (a:x) = Right(a,x)
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-- (2) Ana + cata + hylo -------------------------------------------------------
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base g f = g -|- (g >< f)
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rec f = base id f
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cata g = g . rec (cata g) . out
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ana g = inl . (rec (ana g) ) . g
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hylo h g = cata h . ana g
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-- (3) Examples ----------------------------------------------------------------
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concatg ([],ys) = i1 ys
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concatg (x:xs,ys) = i2([x],(xs,ys))
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concath = either id f
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where f([a],l) = a:l
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glast = cata (either id p2)
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{--
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merge (l,[]) = l
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merge ([],r) = r
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merge (x:xs,y:ys) | x < y = x : merge(xs,y:ys)
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| otherwise = y : merge(x:xs,ys)
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--}
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mrg (l,[]) = i1 l
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mrg ([],r) = i1 r
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mrg (x:xs,y:ys) | x < y = i2(x,(xs,y:ys))
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| otherwise = i2(y,(x:xs,ys))
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