Project 26 — Fibonacci

10
100
QUIT

ek9 fibonacci.ek9 < input.txt

Fibonacci Sequence, by Al Sweigart al@inventwithpython.com

The Fibonacci sequence begins with 0 and 1, and the next number is the
sum of the previous two numbers. The sequence continues forever:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987...

Enter the Nth Fibonacci number you wish to
calculate (such as 5, 50, 1000, 9999), or QUIT to quit:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34

The #10 Fibonacci number is 34
Enter the Nth Fibonacci number you wish to
calculate (such as 5, 50, 1000, 9999), or QUIT to quit:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811, 514229, 832040, 1346269, 2178309, 3524578, 5702887, 9227465, 14930352, 24157817, 39088169, 63245986, 102334155, 165580141, 267914296, 433494437, 701408733, 1134903170, 1836311903, 2971215073, 4807526976, 7778742049, 12586269025, 20365011074, 32951280099, 53316291173, 86267571272, 139583862445, 225851433717, 365435296162, 591286729879, 956722026041, 1548008755920, 2504730781961, 4052739537881, 6557470319842, 10610209857723, 17167680177565, 27777890035288, 44945570212853, 72723460248141, 117669030460994, 190392490709135, 308061521170129, 498454011879264, 806515533049393, 1304969544928657, 2111485077978050, 3416454622906707, 5527939700884757, 8944394323791464, 14472334024676221, 23416728348467685, 37889062373143906, 61305790721611591, 99194853094755497, 160500643816367088, 259695496911122585, 420196140727489673, 679891637638612258, 1100087778366101931, 1779979416004714189, 2880067194370816120, 4660046610375530309, 7540113804746346429, 12200160415121876738, 19740274219868223167, 31940434634990099905, 51680708854858323072, 83621143489848422977, 135301852344706746049, 218922995834555169026

The #100 Fibonacci number is 218922995834555169026
Enter the Nth Fibonacci number you wish to
calculate (such as 5, 50, 1000, 9999), or QUIT to quit:
Thanks for playing!

#!ek9
defines module bigbook.fibonacci

  defines constant

    //The sequence starts from two given terms, 0 and 1. The book prints the answer for those
    //two from fixed text ending in a full stop; every calculated answer has none.
    GivenTerms <- 2

  defines type

    List of BigInteger

  defines class

    //THE input idiom of this book, copied unchanged from lib/LineInput.ek9 (the reasons are
    //there): read with next(), and every input loop also stops when ended() is true.
    LineInput
      stdin as Stdin: Stdin()
      inputEnded as Boolean: false

      next()
        <- rtn as String: stdin.next()
        if not rtn?
          inputEnded: true

      ended() as pure
        <- rtn as Boolean: Boolean(inputEnded)

      override operator ? as pure
        <- rtn as Boolean: true

    //THE INPUT AND OUTPUT: everything the player sees or types goes through here, worded by Say.
    Console
      stdout as Stdout: Stdout()
      input as LineInput: LineInput()
      say as Say: Say("en")

      Console()
        -> words as Say
        say: words

      showIntroduction()
        stdout.println(say.introduction())

      //The term the player asks for; unset when they QUIT or the input ends.
      nextTerm()
        <- rtn as Integer: Integer()
        quitting <- false
        while not rtn? and not quitting and not input.ended()
          stdout.println(say.askTerm())
          if entry <- input.next()
            response <- entry.trim().upperCase()
            if response == say.quit()
              quitting: true
            else
              rtn: termWanted(response)
              if not rtn?
                stdout.println(say.notATerm())

      //Printed one term at a time: 9999 terms make a line of megabytes, too long to build up
      //as a single String first.
      showSeries()
        -> terms as List of BigInteger
        stdout.println("")
        separator <- ""
        for term in terms
          stdout.print(`${separator}${term}`)
          separator: ", "
        stdout.println("")
        stdout.println("")

      showAnswer()
        ->
          nth as Integer
          answer as BigInteger

        stdout.println(isGivenTerm(nth) <- say.givenTerm(nth, answer) : say.calculatedTerm(nth, answer))

      showGoodbye()
        stdout.println(say.goodbye())

      ended() as pure
        <- rtn as Boolean: input.ended()

      override operator ? as pure
        <- rtn as Boolean: true

  defines function

    //THE GAME: the sequence, with no input or output.

    //A term number above 0, or unset for anything else.
    termWanted() as pure
      -> entry as String
      <- rtn as Integer: Integer()
      if term <- Integer(entry) then term > 0
        rtn: term

    //The terms the sequence starts from, rather than calculates.
    isGivenTerm() as pure
      -> nth as Integer
      <- rtn as Boolean: nth <= GivenTerms

    //The first `count` Fibonacci numbers. BigInteger, because the 94th no longer fits in the
    //64 bits of an Integer, and an Integer that overflows becomes unset.
    //`+` makes a new number, so moving the names along never changes a term already stored.
    fibonacciSeries()
      -> count as Integer
      <- rtn as List of BigInteger: List() of BigInteger
      previous <- BigInteger(0)
      current <- BigInteger(1)
      while length rtn < count
        rtn += previous
        following <- previous + current
        previous: current
        current: following

  defines function

    //THE language of the words, copied unchanged from lib/Language.ek9: BIGBOOK_LANG when it
    //is set (fr, zh, ...), otherwise en.
    language()
      <- rtn as String: EnvVars().get("BIGBOOK_LANG") ?: "en"

  //THE WORDS: every word the player sees.
  defines text for "en"

    Say

      introduction()
        `Fibonacci Sequence, by Al Sweigart al@inventwithpython.com

The Fibonacci sequence begins with 0 and 1, and the next number is the
sum of the previous two numbers. The sequence continues forever:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987...
`

      askTerm()
        `Enter the Nth Fibonacci number you wish to
calculate (such as 5, 50, 1000, 9999), or QUIT to quit:`

      quit()
        "QUIT"

      notATerm()
        "Please enter a number greater than 0, or QUIT."

      givenTerm()
        ->
          nth as Integer
          answer as BigInteger
        `The #${nth} Fibonacci number is ${answer}.`

      calculatedTerm()
        ->
          nth as Integer
          answer as BigInteger
        `The #${nth} Fibonacci number is ${answer}`

      goodbye()
        "Thanks for playing!"

  defines program

    //Fibonacci Sequence (Big Book project 26). Prints the first N terms of the sequence and the
    //Nth, for each N typed, until QUIT. The game decides; the Console asks and tells, in the
    //player's words.
    Fibonacci()
      //A language with no words of its own is unset: ?: falls back to English.
      console <- Console(Say(language()) ?: Say("en"))

      console.showIntroduction()
      running <- true
      while running and not console.ended()
        if nth <- console.nextTerm()
          terms <- fibonacciSeries(nth)
          console.showSeries(terms)
          console.showAnswer(nth, terms.getOrDefault(nth - 1, BigInteger()))
        else
          running: false
      //The player quit: the game says goodbye. At the end of the input it does not.
      console.showGoodbye()