pprTerm,
cPprTerm,
cPprTermBase,
+ CustomTermPrinter,
termType,
foldTerm,
TermFold(..),
maybe emptyVarEnv tyVarsOfType mb_ty,
fPrim = \ _ _ -> emptyVarEnv }
where concatVarEnv = foldr plusVarEnv emptyVarEnv
+
----------------------------------
-- Pretty printing of terms
----------------------------------
| otherwise = return$ parens$ ppr n <> text "::" <> ppr ty
pprTermM1 _ = panic "pprTermM1"
-type CustomTermPrinter m = Int -> TermProcessor Term (m (Maybe SDoc))
+-------------------------------------------------------
+-- Custom Term Pretty Printers
+-------------------------------------------------------
+
+-- We can want to customize the representation of a
+-- term depending on its type.
+-- However, note that custom printers have to work with
+-- type representations, instead of directly with types.
+-- We cannot use type classes here, unless we employ some
+-- typerep trickery (e.g. Weirich's RepLib tricks),
+-- which I didn't. Therefore, this code replicates a lot
+-- of what type classes provide for free.
+
+-- Concretely a custom term printer takes an explicit
+-- recursion knot, and produces a list of Term Processors,
+-- which additionally need a precedence value to
+-- either produce a SDoc or fail (and they do this in some monad m).
+
+type Precedence = Int
+type RecursionKnot m = Int-> Term -> m SDoc
+type CustomTermPrinter m = RecursionKnot m
+ -> [Precedence -> TermProcessor Term (m (Maybe SDoc))]
-- Takes a list of custom printers with a explicit recursion knot and a term,
-- and returns the output of the first succesful printer, or the default printer
-cPprTerm :: Monad m =>
- ((Int->Term->m SDoc)->[CustomTermPrinter m]) -> Term -> m SDoc
+cPprTerm :: Monad m => CustomTermPrinter m -> Term -> m SDoc
cPprTerm printers_ = go 0 where
printers = printers_ go
go prec t@(Term ty dc val tt) = do
firstJustM [] = return Nothing
-- Default set of custom printers. Note that the recursion knot is explicit
-cPprTermBase :: Monad m => (Int->Term-> m SDoc)->[CustomTermPrinter m]
+cPprTermBase :: Monad m => CustomTermPrinter m
cPprTermBase y =
[
ifTerm isTupleTy (\ _ _ tt ->