В письме от 27 апреля 2013 18:55:16 пользователь Corentin Dupont написал:
Hi Cafe,can I ask the compiler to display the type of an inferred value during
compile
time?It would be great if I can output a string during compilation with the
type.A little
bit like running :type in GHCi, but without GHCi... Because running GHCi is
sometime
painful (I have to clean my code first).
I'm thinking of something like:
main :: IO ()main = do a <- someCode displayTypeAtCompileTime a return ()
$ ghc -c test.hstest.hs:4:3: your type is: Foo
Thanks,Corentin
Hi.
What about TemplateHaskell? Smth like:
{-# LANGUAGE TemplateHaskell #-}
module DisplayType where
import Language.TH
displayTypeAtCompileTime :: Name -> Q Exp
displayTypeAtComileTime name = do
reified <- reify name
-- inspect reified structure, see TH haddock documentation
runIO $ putStrLn $ show theType
[| undefined |] -- you need to return some expression; since you are not
to use it's
value, it may be even undefined, it seems.
###
{-# LANGUAGE TemplateHaskell #-}
module Main where
import DisplayType
main = do
...
$displayTypeAtCompileTime 'a
...
WBR, Ilya Portnov.
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