Fibonacci sequence: Difference between revisions
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(0, 1)
[1 .. n]</syntaxhighlight>
==== As an unfold ====
Create an infinite list of integers using an unfold. The nth fibonacci number is the nth number in the list.
<syntaxhighlight lang="haskell">import Data.List (unfoldr)
fibs :: [Integer]
fibs = unfoldr (\(x, y) -> Just (x, (y, x + y))) (0, 1)
fib n :: Integer -> Integer
fib n = fibs !! n</syntaxhighlight>
=== With matrix exponentiation ===
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=={{header|langur}}==
<syntaxhighlight lang="langur">
val fibonacci = fn x:if(x < 2: x ; self(x - 1) + self(x - 2))
writeln map
</syntaxhighlight>
{{out}}
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===Binary powering===
This is an efficient method (similar to the one used internally by <code>fibonacci()</code>), although running it without compilation won't give competitive speed.
<syntaxhighlight lang="parigp">fib(n)={
if(n<=0,
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a
};</syntaxhighlight>
===Trigonometric===
This solution uses the complex hyperbolic sine.
<syntaxhighlight lang="parigp">fib(n)=real(2/sqrt(5)/I^n*sinh(n*log(I*(1+sqrt(5))/2)))\/1;</syntaxhighlight>
===Chebyshev===
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