Fuzion • Idioms • Idiom # 301: Recursive Fibonacci sequence

Idiom # 301: Recursive Fibonacci sequence

Naive approach

Code

fib(n i32) i32 =>
  if n<2 then n
  else        (fib (n-1)) + (fib (n-2))

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fib(n i32) i32 =>
  if n<2 then n
  else        (fib (n-1)) + (fib (n-2))
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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What are effects?

Runnable Example

ex301 is
  fib(n i32) i32
    pre n >= 0
  =>
    if n<2 then n
    else        (fib (n-1)) + (fib (n-2))

  for
    i in 0..10
  do
    say "fib $i = {fib i}"

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ex301 is
  fib(n i32) i32
    pre n >= 0
  =>
    if n<2 then n
    else        (fib (n-1)) + (fib (n-2))
  for
    i in 0..10
  do
    say "fib $i = {fib i}"
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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What are effects?

Efficient tail recursive implementation

ex301a is

  fib(n i32)
    pre n >= 0
  =>
    fib_acc(n1, n2, n0 i32) =>
      if n0=0 then n1
      else fib_acc n2 (n1+n2) (n0-1)

    fib_acc 0 1 n

  for
    i in 0..10
  do
    say "fib $i = {fib i}"

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ex301a is
  fib(n i32)
    pre n >= 0
  =>
    fib_acc(n1, n2, n0 i32) =>
      if n0=0 then n1
      else fib_acc n2 (n1+n2) (n0-1)
    fib_acc 0 1 n
  for
    i in 0..10
  do
    say "fib $i = {fib i}"
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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What are effects?

last changed: 2025-05-13

next: Idiom # 302: String interpolation