Re: [Haskell-beginners] Getting a variables type as a string at runtime

If you just wanted the constructor name, show would have worked perfectly. On Sun Jan 12 2014 at 15:45:28, Gareth Morgan wrote:

Data.Typeable with Data.Data worked. Thank you.

Using Typeable alone was only giving me the type of the whole type. Data.Data had the toConstr function needed to give me the particular constructor name.

For reference if anyone is interested in the solution:

import Data.Typeable import Data.Data

data A = A | B | C deriving (Typeable, Data)

typeName :: A -> String typeName = show . toConstr

I needed to add DeriveDataTypeable extension to my cabal file

On Sun, Jan 12, 2014 at 2:53 PM, Brandon Allbery wrote:

On Sun, Jan 12, 2014 at 9:47 AM, Gareth Morgan wrote:

Won't show include all the components? I wanted to include only the type name.

Types only exist at compile time normally. But if you add a Typeable constraint (see Data.Typeable and the DeriveDataTypeable extension) you can get type names at runtime.

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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