1 files changed, 19 insertions, 3 deletions
diff --git a/src/Language/SimpleShell/Parser.hs b/src/Language/SimpleShell/Parser.hs
index dd65ffe..d75602b 100644
--- a/src/Language/SimpleShell/Parser.hs
+++ b/src/Language/SimpleShell/Parser.hs
@@ -3,8 +3,10 @@
 module Language.SimpleShell.Parser
   ( Parser
   , lexeme
+  , symbol
   , lookupVar
   , lookupFun
+  , declareVars
   , initContext
   , parseTest
   )
@@ -12,18 +14,22 @@ where
 
 
 import Language.SimpleShell.AST.Name (FunName, VarName)
-import Language.SimpleShell.AST.SimpleType (SimpleType, FunSig)
+import Language.SimpleShell.AST.SimpleType (SimpleType, FunSig, Typed)
 
-import Control.Monad.Reader (ask, ReaderT, runReaderT)
+import Control.Monad (void)
+import Control.Monad.Reader (ask, local, ReaderT, runReaderT)
+import Data.List (nub)
 import Data.Map (Map)
-import qualified Data.Map as Map (empty, lookup)
+import qualified Data.Map as Map (empty, lookup, fromList)
 import Data.Text (Text, unpack)
+import Data.Tuple (swap)
 import Data.Void (Void)
 import Text.Megaparsec (Parsec)
 import qualified Text.Megaparsec as MP (parseTest)
 import Text.Megaparsec.Char (space1)
 import qualified Text.Megaparsec.Char.Lexer as L
   ( lexeme
+  , symbol
   , space
   , skipLineComment
   , skipBlockComment
@@ -53,6 +59,9 @@ sc = L.space
 lexeme :: Parser a -> Parser a
 lexeme = L.lexeme sc
 
+symbol :: Text -> Parser ()
+symbol = void . L.symbol sc
+
 
 lookupVar :: VarName -> Parser SimpleType
 lookupVar varname = do
@@ -68,6 +77,13 @@ lookupFun fname = do
     Just sig -> return sig
     Nothing  -> fail $ "Undefined function " ++ unpack fname
 
+declareVars :: [Typed VarName] -> Parser a -> Parser a
+declareVars decls p = do
+  let names = map snd decls
+  if length (nub names) == length names   -- TODO: inefficient
+  then local (\ctx -> ctx { ctxVars = Map.fromList $ map swap decls }) p
+  else fail "Duplicate variable name."
+
 
 parseTest :: Show a => Parser a -> Text -> IO ()
 parseTest p = MP.parseTest (runReaderT p initContext)