FizzBuzz (Erlang)
From LiteratePrograms
FizzBuzz is a common exercise program, such as Hello, world! or 99 Bottles of Beer. It is based on a common game of the same name. The program prints a series of natural numbers, substituting those divisible by 3 with "Fizz", those divisible by 5 with "Buzz" and those divisible by both 3 and 5 with "FizzBuzz".
The interface to our Erlang implementation of FizzBuzz is a a single argument function called fizzbuzz. The fizzbuzz function will print FizzBuzz values for the first N natural numbers. The argument to the function specifies the value of N.
<<fizzbuzz.erl>>= -module(fizzbuzz). -export([fizzbuzz/1]). initialization rules termination
To implement FizzBuzz in Erlang, we use a tail-recursive loop. We'll need two variables: a loop counter and the maximum number of iterations. We initialize the loop counter to 1 (the first natural number), and set the maximum number of iterations to the value of N passed by the caller.
<<initialization>>= fizzbuzz(N) -> fizzbuzz(1, N).
The heart of our implementation is the fizzbuzz/2 function, which implements the tail-recursive loop. At each iteration, fizzbuzz/2 checks the current value of the loop counter I against the FizzBuzz rules, and prints a corresponding message.
<<rules>>= fizzbuzz(I, N) when I =< N -> if I rem 15 =:= 0 -> io:format("FizzBuzz~n"); I rem 3 =:= 0 -> io:format("Fizz~n"); I rem 5 =:= 0 -> io:format("Buzz~n"); true -> io:format("~p~n", [ I ]) end, fizzbuzz(I+1, N);
The tail-recursive loop halts when the loop counter is greater than the maximum number of iterations.
<<termination>>= fizzbuzz(_, _) -> ok.
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