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16 lines
524 B
Haskell
16 lines
524 B
Haskell
-- fib.hs — infinite Fibonacci stream.
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--
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-- The classic two-line definition: `fibs` is a self-referential
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-- lazy list built by zipping itself with its own tail, summing the
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-- pair at each step. Without lazy `:` (cons cell with thunked head
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-- and tail) this would diverge before producing any output; with
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-- it, `take 15 fibs` evaluates exactly as much of the spine as
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-- demanded.
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zipPlus (x:xs) (y:ys) = x + y : zipPlus xs ys
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zipPlus _ _ = []
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myFibs = 0 : 1 : zipPlus myFibs (tail myFibs)
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result = take 15 myFibs
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