Template Haskell でコンパイル時 FizzBuzz

FizzBuzz.hs

{-# LANGUAGE TemplateHaskell #-}

module FizzBuzz where

import Language.Haskell.TH

fizzbuzz :: Int -> ExpQ
fizzbuzz 0 = [| putStrLn "FizzBuzz" |]
fizzbuzz n = appE (appE (varE (mkName ">>"))
                        (fizzbuzz (n - 1)))
                  x where
                      x :: ExpQ
                      x
                        | n `mod` 15 == 0 = [| putStrLn "FizzBuzz" |]
                        | n `mod` 3  == 0 = [| putStrLn "Fizz" |]
                        | n `mod` 5  == 0 = [| putStrLn "Buzz" |]
                        | otherwise       = [| print n |]

Main.hs

{-# LANGUAGE TemplateHaskell #-}

module Main where

import FizzBuzz

main = $(fizzbuzz 15)