Re: [Haskell-cafe] Remove redundancy with Template Haskell

argh, always forget to reply to all It's possible, just somewhat painful because TH /requires/ you to build an AST -- you can't just return a string representing what you want to splice in. Here's one using haskell-src-meta: {-# LANGUAGE TemplateHaskell #-} import Language.Haskell.TH import Language.Haskell.Meta call :: Name -> String -> Q Exp call name exp' = case parseExp exp' of Right expr -> let fun = [| name |] str = stringE exp' in [| $fun $(return expr) $str |] _ -> error "Invalid expression." This can be then used to make a QuasiQuoter: call' :: QuasiQuoter call' = QuasiQuoter { quoteExp = call 'functionYouWantHere } On Fri, Mar 29, 2013 at 8:40 AM, Corentin Dupont wrote:

Thanks Daniel, that's very simple!

Realizing this in TH seems be impossible, is it right?

On Wed, Mar 27, 2013 at 10:33 PM, Daniel Trstenjak wrote:

...

Hi Corentin,

On Wed, Mar 27, 2013 at 09:13:41PM +0100, Corentin Dupont wrote:

...

I have a function that looks like this: call :: SomeFunction -> String -> SomeState

The string is actually the representation of the function passed in parameter. It is stored in the state for documentation. So a call looks like that: call (\a -> putStrLn a) "\a -> putStrLn a"

There is a clear redundancy here, how could I remove it with Template Haskell? I cannot figure out...

You can even use cpp to get something like:

#define CALL(func) call (func) #func

CALL(\a -> a + 1) => call (\a -> a + 1) "\a -> a + 1"

Greetings, Daniel

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