tame the strings

Adds a PrettyPrint typeclass which operates on Text and should replace
Show, since constantly converting strings from linked lists to arrays
seems somewhat silly.

1 files changed, 24 insertions, 14 deletions

diff --git a/lib/Util.hs b/lib/Util.hs
index be67143..3a0e1d4 100644
--- a/lib/Util.hs
+++ b/lib/Util.hs
@@ -1,27 +1,37 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE LambdaCase        #-}
 {-# LANGUAGE OverloadedStrings #-}
 
-
+-- | has (perhaps inevitably) morphed into a module that mostly
+-- concerns itself with wrangling haskell's string types
 module Util where
 
-import Data.Text (Text)
-import Data.Text as T
-import Data.Aeson as Aeson
+import           Data.Aeson as Aeson
+import           Data.Text  (Text)
+import           Data.Text  as T
 
 -- | haskell's many string types are FUN …
 showText :: Show a => a -> Text
 showText = T.pack . show
 
--- | same as showText, but without the "String"-prefix for strings
--- TODO: serialise back into json for printing? People may get
--- confused by the type annotations if they only know json …
-showAeson :: Aeson.Value -> Text
-showAeson (Aeson.String s) = showText s
-showAeson v = showText v
-
+-- | a class to address all the string conversions necessary
+-- when using Show to much that just uses Text instead
+class PrettyPrint a where
+  prettyprint :: a -> Text
 
+-- | let's see if this is a good idea or makes type inference bite us
+instance PrettyPrint Text where
+  prettyprint text = "\"" <> text <> "\""
 
+-- | same as show json, but without the "String" prefix for json strings
+instance PrettyPrint Aeson.Value where
+  prettyprint = \case
+    Aeson.String s -> prettyprint s
+    v              -> (T.pack . show) v
 
+-- | here since Unit is sometimes used as dummy type
+instance PrettyPrint () where
+  prettyprint _ = error "shouldn't pretty-print Unit"
 
--- | adds quotes (but does not escape, for now!)
-quote :: Text -> Text
-quote text = "\"" <> text <> "\""
+printPretty :: PrettyPrint a => a -> IO ()
+printPretty = putStr . T.unpack . prettyprint