Re: [Haskell-cafe] reasons why Template Haskell does not propose something similar to Python exec() or eval()

24 Aug 2013


      Tobias Dammers wrote:
...
IIRC you can use haskell-src-exts to parse a string into TH AST
structures. There might even be a quasi-quoter for that; I don't have a
real computer at hand right more, so you'll need to do some research of
your own.
...
:m Language.Haskell.Meta
parseDecs "s=s+1"
Right [ValD (VarP s) (NormalB (UInfixE (VarE s) (VarE +) (LitE (IntegerL 
1)))) []]
parseExp "x+1"
Right (UInfixE (VarE x) (VarE +) (LitE (IntegerL 1)))
:i parseDecs
...
:i parseExp
Thanks Tobias, it led me to the right path. There is indeed a solution in 
Language.Haskell.Meta:

$ ghci
parseDecs ::
  String -> Either String [Language.Haskell.TH.Syntax.Dec]
        -- Defined in `Language.Haskell.Meta.Parse'
parseExp :: String -> Either String Language.Haskell.TH.Syntax.Exp
        -- Defined in `Language.Haskell.Meta.Parse'

Thanks,

TP