A fast, recursive, typed fibonacci program written in Racket.

fib.rkt

#lang typed/racket

(: fib (-> Number Number))
(define (fib n)
  (fib-iter 0 1 n))

(: fib-iter (-> Number Number Number Number))
(define (fib-iter a b n)
  (if (= n 0) a
    (fib-iter b (+ a b) (- n 1))))

(define nth (command-line #:args (#{nth : String}) (string->number nth)))

(if (number? nth)
  (fib nth)
  (displayln "Please provide a number as an argument."))

x-example.md

time -p racket fib.rkt 100000 | wc -c
real 0.66
user 0.59
sys 0.06
20900

Not too shabby considering typed/racket incurs quite an overhead. This is after compiling to bytecode.

raco make fib.rkt