Add simplification module

Author: ollef

src/Language/Elm/Expression.hs

@@ -11,6 +11,7 @@ module Language.Elm.Expression where
 import Protolude
 
 import Bound
+import Bound.Var (unvar)
 import Data.Bifoldable
 import Data.Eq.Deriving
 import Data.Ord.Deriving
@@ -104,6 +105,25 @@ if_ bool_ true false =
 tuple :: Expression v -> Expression v -> Expression v
 tuple e1 e2 = apps "Basics.," [e1, e2]
 
+lets :: Eq b => [(b, Expression v)] -> Scope b Expression v -> Expression v
+lets =
+  go (panic "Language.Elm.Expression.lets unbound var") identity
+  where
+    go :: Eq b => (b -> v') -> (v -> v') -> [(b, Expression v)] -> Scope b Expression v -> Expression v'
+    go boundVar freeVar bindings scope =
+      case bindings of
+        [] ->
+          unvar boundVar freeVar <$> fromScope scope
+
+        (v, e):bindings' ->
+          Let (freeVar <$> e) $
+            toScope $
+            go
+              (\b -> if b == v then B () else F $ boundVar b)
+              (F . freeVar)
+              bindings'
+              scope
+
 foldMapGlobals
   :: Monoid m
   => (Name.Qualified -> m)

src/Language/Elm/Name.hs

@@ -4,11 +4,13 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ViewPatterns #-}
 module Language.Elm.Name where
 
 import Protolude
 
 import Data.String
+import qualified Data.Char as Char
 import qualified Data.Text as Text
 
 type Module = [Text]
@@ -21,6 +23,21 @@ newtype Local = Local Text
 data Qualified = Qualified Module Text
   deriving (Eq, Ord, Show, Generic, Hashable)
 
+isConstructor :: Qualified -> Bool
+isConstructor name =
+  case name of
+    "List.::" ->
+      True
+
+    "Basics.," ->
+      True
+
+    Qualified _ (Text.uncons -> Just (firstChar, _)) ->
+      Char.isUpper firstChar
+
+    _ ->
+      False
+
 instance IsString Qualified where
   fromString s =
     case unsnoc $ Text.splitOn "." $ fromString s of