Extract common parsing code

code/cs325-langs/src/LanguageOne.hs

@@ -1,5 +1,6 @@
 module LanguageOne where
 import qualified PythonAst as Py
+import qualified CommonParsing as P
 import Data.Bifunctor
 import Data.Char
 import Data.Functor
@@ -54,31 +55,8 @@ data Prog = Prog [Function]
 {- Parser -}
 type Parser = Parsec String (Maybe Int)
 
-parseInt :: Parser Int
-parseInt = read <$> (many1 digit <* spaces)
-
 parseVar :: Parser String
-parseVar =
-    do
-        c <- satisfy (\c -> (isLetter c && isLower c) || c == '_')
-        cs <- many (satisfy isLetter <|> digit)
-        spaces
-        let var = c:cs
-        if var `elem` ["if", "then", "else", "rand"]
-        then fail "reserved"
-        else return var
-
-parseKwIf :: Parser ()
-parseKwIf = string "if" $> ()
-
-parseKwThen :: Parser ()
-parseKwThen = string "then" $> ()
-
-parseKwElse :: Parser ()
-parseKwElse = string "else" $> ()
-
-parseKwRand :: Parser Expr
-parseKwRand = string "rand" $> Random
+parseVar = P.var ["if", "then", "else", "var"]
 
 parseThis :: Parser Expr
 parseThis =
@@ -127,11 +105,11 @@ parseSelector =
 parseIfElse :: Parser Expr
 parseIfElse =
     do
-        parseKwIf >> spaces
+        P.kwIf >> spaces
         ec <- parseExpr
-        spaces >> parseKwThen >> spaces
+        spaces >> P.kwThen >> spaces
         et <- parseExpr
-        spaces >> parseKwElse >> spaces
+        spaces >> P.kwElse >> spaces
         ee <- parseExpr
         spaces
         return $ IfElse ec et ee
@@ -162,7 +140,7 @@ parseParenthesized =
 
 parseBasicExpr :: Parser Expr
 parseBasicExpr = choice
-    [ IntLiteral <$> parseInt
+    [ IntLiteral <$> P.int
     , parseThis
     , parseList
     , parseSplit
@@ -170,7 +148,7 @@ parseBasicExpr = choice
     , parseParameter
     , parseParenthesized
     , Var <$> try parseVar
-    , parseKwRand
+    , P.kwRand $> Random
     , parseIfElse
     ] 
 
@@ -203,33 +181,16 @@ parsePostfixedExpr =
         ps <- many parsePostfix
         return $ foldl (flip ($)) eb ps
 
-parseOp :: String -> Op -> Parser Op
-parseOp s o = try (string s) >> return o
-
-parseLevel :: Parser Expr -> Parser Op -> Parser Expr
-parseLevel pe po =
-    do
-        start <- pe
-        spaces
-        ops <- many $ try $ do
-            op <- po
-            spaces
-            val <- pe
-            spaces
-            return (op, val)
-        spaces
-        return $ foldl (\l (o, r) -> BinOp o l r) start ops
-
 parseExpr :: Parser Expr
-parseExpr = foldl parseLevel parsePostfixedExpr
-    [ parseOp "*" Multiply, parseOp "/" Divide
-    , parseOp "+" Add, parseOp "-" Subtract
-    , parseOp "<<" Insert
-    , parseOp "++" Concat
-    , parseOp "<=" LessThanEq <|> parseOp ">=" GreaterThanEq <|>
-        parseOp "<" LessThan <|> parseOp ">" GreaterThan <|>
-        parseOp "==" Equal <|> parseOp "!=" NotEqual
-    , parseOp "&&" And <|> parseOp "||" Or
+parseExpr = P.precedence BinOp parsePostfixedExpr
+    [ P.op "*" Multiply, P.op "/" Divide
+    , P.op "+" Add, P.op "-" Subtract
+    , P.op "<<" Insert
+    , P.op "++" Concat
+    , try (P.op "<=" LessThanEq) <|> try (P.op ">=" GreaterThanEq) <|>
+        P.op "<" LessThan <|> P.op ">" GreaterThan <|>
+        P.op "==" Equal <|> P.op "!=" NotEqual
+    , P.op "&&" And <|> P.op "||" Or
     ]
 
 parseFunction :: Parser Function