Functional Fizz Buzz

Fizz-Buzz or Bizz Buzz is a word game, popularized by Jeff Atwood in the article:

Why Can’t Programmers… Program?

The game has been turned into a simple programming test:

Write a program that prints the numbers from 1 to 100. But for multiples of 3 print "Fizz" instead of the number and for the multiples of 5 print "Buzz". For numbers which are multiples of both 3 and 5 print "FizzBuzz".

If you’re involved in hiring programmers then the article is probably worth a read.

This kind of problem can be expressed very concisely in functional programming languages to the point where the code fits in a tweet.

Haskell

Last month Calvin Bottoms posted an article describing and implementation of Fizz-Buzz in Haskell expressed in a mere 78 characters:

[max(show x)(concat[n|(f,n)<-[(3,"Fizz"),(5,"Buzz")],mod x f==0])|x<-[1..100]]

Higher order functions and list comprehensions (a feature taken from Miranda) make this very terse, but also a little impenetrable.

F#

Rather more verbose (122 characters) but perhaps a little more readable:

for n in 1..100 do printfn "%s" <| match n%3, n%5 with 

0,0 -> "FizzBuzz" | 0,_ -> "Fizz" | _,0 -> "Buzz" | _,_ -> string n

Pattern matching makes the various states relatively obvious.

Clojure

Martin Trojer sent over this quite elegant Clojure implementation via Twitter:

(map #(cond (zero? (mod % 15)) "FizzBuzz" (zero? (mod % 3)) "Fizz" 

(zero? (mod % 5)) "Buzz" :else %) (range 1 101))

Testing for “FizzBuzz” using modulus 15 helps reduce the character count.

Erlang

I’ve been playing with Erlang recently and Fizz-Buzz is my new “Hello World” app. This was my first effort:

f(101)->ok;

f(X)->Y=case{X rem 3,X rem 5}of{0,0}->fizzbuzz;{0,_}->fizz;{_,0}->buzz;

{_,_}->X end,io:format("~w~n",[Y]),f(X+1). 

Erlang doesn’t have a for loop construct built-in so I resorted to recursion instead.

That said you can achieve the same thing using the lists module seq and foreach functions:

lists:foreach(fun(X)->io:format("~w~n",[case{X rem 3,X rem 5}of{0,0}->fizzbuzz;

{0,_}->fizz;{_,0}->buzz;{_,_}->X end])end,lists:seq(1,100)).

Next?

Is Fizz-Buzz the new “Hello World”?

I think it might be, despite Jeff’s protestations, take a peek at Fizz-Buzz on Rosetta Code.