[Haskell-cafe] Problems with Language.Haskell.Interpreter and
dgorin at dc.uba.ar
Tue Sep 29 10:16:50 EDT 2009
On Sep 29, 2009, at 8:56 AM, Martin Hofmann wrote:
> 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
> 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
>> :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...
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!
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