FizzBuzz¶

The classic FizzBuzz problem solved in Endo using let-in bindings and guarded match arms.

// Classic FizzBuzz using let-in bindings and guarded match arms

let fizzbuzz n =
    let by3 = n % 3 in
    let by5 = n % 5 in
    match 0 with
    | _ when by3 == 0 && by5 == 0 -> "FizzBuzz"
    | _ when by3 == 0 -> "Fizz"
    | _ when by5 == 0 -> "Buzz"
    | _ -> string_of_int n

println (fizzbuzz 1)
println (fizzbuzz 2)
println (fizzbuzz 3)
println (fizzbuzz 4)
println (fizzbuzz 5)
println (fizzbuzz 6)
println (fizzbuzz 7)
println (fizzbuzz 10)
println (fizzbuzz 15)
println (fizzbuzz 30)

Key Techniques¶

• Let-in bindings (let by3 = n % 3 in ...) precompute intermediate values in a scoped expression. The bindings by3 and by5 are only visible within the match body.
• Guard-only matching -- the match scrutinee is a dummy value (0), and all logic lives in when guards. This is a common pattern when decisions depend on multiple conditions rather than a single value's structure.
• Guard ordering matters: the by3 == 0 && by5 == 0 arm must come first because match arms are evaluated top-to-bottom, and the combined case must be checked before the individual ones.
• string_of_int converts an integer to its string representation, used here for the default case where the number is neither Fizz nor Buzz.
• This example shows that even simple programming exercises benefit from Endo's concise functional style -- the entire solution is a single function with no mutable state.

See Also¶

• Pattern Matching
• Variables & Bindings
• Functions