On Sep 29, 2009, at 8:56 AM, Martin Hofmann wrote:
Hi,
The API of Language.Haskell.Interpreter says, that 'runInterpreter'
runInterpreter :: (MonadCatchIO m, Functor m) => InterpreterT m a -> m (Either InterpreterError a)
returns 'Left' in case of errors and 'GhcExceptions from the underlying GHC API are caught and rethrown as this'.
What kind of errors do a generate here, why are they not caught by runInterpreter and how can I catch them? I assumed to get a 'Left InterpreterError' from the first and an error in MonadCatchIO in the second.
:m +Language.Haskell.Interpreter let estr1 = "let lst [a] = a; lst _ = error \"foo\" in lst []" let estr1 = "let lst [a] = a; in lst []" runInterpreter (setImportsQ [("Prelude", Nothing)] >> eval estr1 ) Right "*** Exception: foo runInterpreter ( eval estr2) Right "*** Exception: <interactive>:1:101-111: Non-exhaustive patterns in function lst
Thanks a lot
InterpreterErrors are those that prevent your to-be-interpreted code from "compiling/typechecking". In this case, estr1 is interpreted just fine; but the interpreted value is an exception. So I think Ritght... is ok. You ought to be able to add a Control.Monad.CatchIO.catch clause to your interpreter to catch this kind of errors, if you want. I just tried it and failed, though, so this is probably a bug. I'll try to track it down in more detail. Thanks for the report! Daniel