CODEWITHSUNDEEP
haskelltemplate-haskell
Vlad the Impala
Vlad the Impala

Reputation: 15872

Multiple function definitions with template haskell

Suppose I have a data type like so:

data Color = Red | Blue | Green

How would I generate a function like this using templatehaskell?

myShow Red   = ...
myShow Blue  = ...
myShow Green = ...

i.e. I'm looking for multiple definitions for a function based on pattern-matching.

Upvotes: 7

Views: 172

Answers (1)

user2407038
user2407038

Reputation: 14578

{-# LANGUAGE TemplateHaskell #-}

module Test where 

import Language.Haskell.TH

data Color = Red | Blue | Green

myShow' :: Q [Dec]
myShow' = return [FunD (mkName "myShow") [mkClause 'Red, mkClause 'Blue, mkClause 'Green]]
  where mkClause n = Clause [ConP n []] (NormalB $ LitE $ StringL $ nameBase n) []

Upvotes: 3

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