Generate a function using Template Haskell

Question

Is it possible to define a function using Template Haskell? For example

convertStringToValue :: String -> Int
convertStringToValue \"three\" = 3
convertStrin         


        

Answer 1

Yes

import Language.Haskell.TH

generateDict :: String -> [(String, Int)] -> Q [Dec]
generateDict fname sns = do
    let clauses = map clause sns
    return $ [FunD (mkName fname) clauses]
        where clause (s,n) =
                Clause [LitP . IntegerL $ toInteger  n]
                       (NormalB . LitE $ StringL s )
                       []

And then

generateDict "myDict" $ zip (words "One Two Tree Four") [1..]

myDict 1 -- => "One"