add initial parser

parser.hs

@@ -0,0 +1,85 @@
+module Parser where
+
+import Text.Parsec
+import Text.Parsec.String
+import Text.Parsec.Expr
+import qualified Text.Parsec.Token as T
+import Text.Parsec.Language
+import AST
+
+languageDef = emptyDef {T.commentStart="{-",
+						  T.commentEnd="-}",
+						  T.commentLine="--",
+						  T.nestedComments=True,
+						  T.identStart = letter <|> char '_',
+						  T.identLetter = alphaNum <|> char '_',
+						  T.reservedNames = ["do", "end", "(", ")", ";", "."],
+						  T.reservedOpNames = ["+", "*"]}
+
+lexer = T.makeTokenParser languageDef
+exprparser = buildExpressionParser ops term <?> "expression"
+ops = [ [Infix (reservedOp "*" >> return Mul) AssocLeft ]
+	  , [Infix (reservedOp "+" >> return Add) AssocLeft]
+	  ]
+
+identifier = T.identifier lexer -- parses an identifier
+reserved   = T.reserved   lexer -- parses a reserved name
+reservedOp = T.reservedOp lexer -- parses an operator
+parens     = T.parens     lexer -- parses surrounding parenthesis
+integer    = T.integer    lexer -- parses an integer
+semi       = T.semi       lexer -- parses a semicolon
+whiteSpace = T.whiteSpace lexer -- parses whitespace
+symbol	   = T.symbol lexer
+
+statement =
+  do
+	e <- exprparser
+	-- char ';'
+	return e 
+
+block = do
+	reserved "do"
+	lst <- seqStmt
+	reserved "end"
+	return $ Block lst
+
+funDef = do
+	name <- identifier
+	reserved "("
+	reserved ")"
+	reserved "->"
+	lst <- exprparser
+	return $ rewriteFun (FunDef name (UnitP, lst))
+
+-- curry FunDef to a definition of lambdas
+rewriteFun (FunDef name (pattern, body)) =
+	Def name $ Lambda [(pattern, [body])]
+
+call = do
+	name <- identifier
+	whiteSpace
+	char '('
+	char ')'
+	whiteSpace
+	return $ Call name [UnitConst]
+
+term = block
+	 <|> try funDef
+	 <|> try call
+	 <|> parens exprparser
+	 <|> fmap Var identifier
+	 <|> fmap IntConst integer
+
+manyExpr = many1 exprparser
+
+seqStmt = do
+	lst <- sepBy1 statement semi
+	return lst
+
+program =
+	many1 $ do
+		e <- exprparser
+		reserved "."
+		return e
+
+parseProgram = parse program "program"