Hi Mike!
I'm not sure what's going on here. When I run that code with LText, with
the string "hi" (instead of reading motd), I get an "out of memory"
exception. So, I don't think this is an issue with lazy IO.
However, storing values produced by an interpreter session reminds me of
Chris's foreign-store package. Might be worth a shot:
http://hackage.haskell.org/package/foreign-store
-Michael
On Tue, May 26, 2015 at 10:47 AM, Mike Meyer
No answer on -beginners, so I'm trying -cafe.
I'm trying to run interpreted code via ClassyPrelude, and getting some results that make me suspect a bug in the Prelude's type system. Or maybe the interpreter.
Anyway, here's a bit of code that works as expected:
{-# LANGUAGE NoImplicitPrelude #-}
import ClassyPrelude import Language.Haskell.Interpreter
main :: IO () main = do fun <- runInterpreter $ makeFun "reverse" case fun of Left e -> print e Right f -> readFile "/etc/motd" >>= hPut stdout . f
makeFun expr = do set [languageExtensions := [NoImplicitPrelude]] setImportsQ [("ClassyPrelude", Nothing)] interpret expr (as :: Text -> Text)
I don't think I can simplify this any further. It works as expected, and also works as expected, and prints out the contents of /etc/motd reversed.
However, if you change the type signature in the last line from Text -> Text to LText -> Ltext (to get lazy text), you get no output. But if you change the function in the first line after main from "reverse" to "id", it works.
So far, it might be an issue with lazy IO. However, change the type signature in the last line to LText -> Text. In this case, there is no output for either value of the expression. I expect an error in this case, as neither id nor reverse should be able to have the type LText -> Text!
So, is there something I missed in either ClassyPrelude or the Interpreter? Or is this a subtle interaction, in which case can someone suggest a workaround? Or have I found a bug in one of the two?
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