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lagenorhynque/Factorial.hs

Created June 3, 2025 06:47
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Factorial and Fibonacci functions in Haskell, Scala, Clojure and Elixir
Raw
factorial.clj
(ns factorial)
(defn factorial [n]
(if (zero? n)
1
(*' n (factorial (dec' n)))))
(defn factorial-seq []
(reductions *' 1 (iterate inc' 1)))
Raw
factorial.ex
defmodule Factorial do
def factorial(0), do: 1
def factorial(n), do: n * factorial(n - 1)
def factorial_seq do
Stream.concat(
[1],
Stream.scan(Stream.from_index(1), &*/2)
)
end
end
Raw
Factorial.hs
module Factorial where
factorial :: Integral a => a -> a
factorial 0 = 1
factorial n = n * factorial (n - 1)
factorialSeq :: Integral a => [a]
factorialSeq = scanl (*) 1 [1..]
Raw
Factorial.scala
object Factorial:
def factorial(n: Int): BigInt = n match
case 0 => 1
case _ => n * factorial(n - 1)
def factorialSeq: LazyList[BigInt] =
LazyList.from(1).scanLeft(BigInt(1))(_ * _)
Raw
fibonacci.clj
(ns fibonacci)
(defn fib [n]
(case n
0 0
1 1
(+' (fib (-' n 1))
(fib (-' n 2)))))
(defn fib-seq []
(->> [0 1]
(iterate (fn [[a b]] [b (+' a b)]))
(map first)))
Raw
fibonacci.ex
defmodule Fibonacci do
def fib(0), do: 0
def fib(1), do: 1
def fib(n), do: fib(n - 1) + fib(n - 2)
def fib_seq do
{0, 1}
|> Stream.iterate(fn {a, b} -> {b, a + b} end)
|> Stream.map(&elem(&1, 0))
end
end
Raw
Fibonacci.hs
module Fibonacci where
fib :: Integral a => a -> a
fib 0 = 0
fib 1 = 1
fib n = fib (n - 1) + fib (n - 2)
fibSeq :: Integral a => [a]
fibSeq = map fst $ iterate (\(a, b) -> (b, a + b)) (0, 1)
Raw
Fibonacci.scala
object Fibonacci:
def fib(n: Int): BigInt = n match
case 0 => 0
case 1 => 1
case _ => fib(n - 1) + fib(n - 2)
def fibSeq: LazyList[BigInt] =
LazyList.iterate((BigInt(0), BigInt(1))) { case (a, b) => (b, a + b) }
.map(_(0))
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