Rename Parse.hs to Lex.hs, to serpate lexing and parsing

1 files changed, 141 insertions, 0 deletions

diff --git a/src/SPL/Lex.hs b/src/SPL/Lex.hs
new file mode 100644
index 0000000..23a697d
--- /dev/null
+++ b/src/SPL/Lex.hs
@@ -0,0 +1,141 @@
+-- vim: et ts=2 sw=2 ai:
+{-# LANGUAGE LambdaCase #-}
+module SPL.Lex
+where
+
+import Prelude hiding(lex)
+
+import Control.Applicative
+import Control.Monad
+import Data.Char
+import Data.List.Utils
+
+data Token
+  = TIdent String
+  | TInt Int
+  | TChar Char
+  | TBool Bool
+
+  | TParenOpen
+  | TParenClose
+  | TBrackOpen
+  | TBrackClose
+  | TBraceOpen
+  | TBraceClose
+  | TDoubleColon
+  | TEquals
+  | TSemicolon
+  | TDot
+  | TComma
+
+  | TIf
+  | TWhile
+  | TReturn
+  | TVar
+  | TVoidType
+  | TCharType
+  | TBoolType
+  | TIntType
+
+  | TPlus
+  | TMinus
+  | TAsterisk
+  | TSlash
+  | TPercent
+  | TEqEq
+  | TLt
+  | TGt
+  | TLtEq
+  | TGtEq
+  | TExclamEq
+  | TAmpAmp
+  | TPipePipe
+  | TColon
+  | TExclam
+
+  | TSingleComment String
+  | TBlockComment String
+  deriving (Show)
+
+lex :: (Monad m, Alternative m) => String -> m [Token]
+lex [] = pure []
+lex (c:s) | isSpace c = lex s
+lex s = (comment s <|> item s <|> int s <|> char s <|> bool s <|> ident s) >>=
+  \(t,s') -> lex s' >>= \ts -> pure (t:ts)
+  where
+    ident :: (Alternative m) => String -> m (Token, String)
+    ident (c:s)
+      | isAlpha c = pure (TIdent (c:cs), s')
+      | otherwise = empty
+      where (cs,s') = span isIdentChar s
+
+    int :: (Alternative m) => String -> m (Token, String)
+    int (c:s)
+      | isDigit c = pure (TInt $ read (c:cs), s')
+      | otherwise = empty
+      where (cs,s') = span isDigit s
+
+    char :: (Alternative m) => String -> m (Token, String)
+    char ('\'':c:'\'':s) = pure (TChar c, s)
+    char _ = empty
+
+    bool :: (Alternative m) => String -> m (Token, String)
+    bool ('F':'a':'l':'s':'e':s) = noIdentifier (TBool False) s
+    bool ('T':'r':'u':'e':s) = noIdentifier (TBool True) s
+    bool _ = empty
+
+    comment :: (Alternative m) => String -> m (Token, String)
+    comment ('/':'/':s) = pure (TSingleComment cs, s')
+      where
+        (cs, s') = span (/= '\n') s
+    comment ('/':'*':s) = pure (TBlockComment cs, s')
+      where
+        (cs, _:_:s') = spanList (\case
+          ('*':'/':s) -> False
+          _           -> True) s
+    comment _ = empty
+
+    item :: (Alternative m) => String -> m (Token, String)
+    item ('i':'f':s) = noIdentifier TIf s
+    item ('w':'h':'i':'l':'e':s) = noIdentifier TWhile s
+    item ('r':'e':'t':'u':'r':'n':s) = noIdentifier TReturn s
+    item ('v':'a':'r':s) = noIdentifier TVar s
+    item ('V':'o':'i':'d':s) = noIdentifier TVoidType s
+    item ('C':'h':'a':'r':s) = noIdentifier TCharType s
+    item ('B':'o':'o':'l':s) = noIdentifier TBoolType s
+    item ('I':'n':'t':s) = noIdentifier TIntType s
+    item ('=':'=':s) = pure (TEqEq, s)
+    item ('<':'=':s) = pure (TLtEq, s)
+    item ('>':'=':s) = pure (TGtEq, s)
+    item ('!':'=':s) = pure (TExclamEq, s)
+    item ('&':'&':s) = pure (TAmpAmp, s)
+    item ('|':'|':s) = pure (TPipePipe, s)
+    item ('(':s) = pure (TParenOpen, s)
+    item (')':s) = pure (TParenClose, s)
+    item ('[':s) = pure (TBrackOpen, s)
+    item (']':s) = pure (TBrackClose, s)
+    item ('{':s) = pure (TBraceOpen, s)
+    item ('}':s) = pure (TBraceClose, s)
+    item ('=':s) = pure (TEquals, s)
+    item (';':s) = pure (TSemicolon, s)
+    item ('.':s) = pure (TDot, s)
+    item (',':s) = pure (TComma, s)
+    item ('+':s) = pure (TPlus, s)
+    item ('-':s) = pure (TMinus, s)
+    item ('*':s) = pure (TAsterisk, s)
+    item ('/':s) = pure (TSlash, s)
+    item ('%':s) = pure (TPercent, s)
+    item ('<':s) = pure (TLt, s)
+    item ('>':s) = pure (TGt, s)
+    item (':':s) = pure (TColon, s)
+    item ('!':s) = pure (TExclam, s)
+    item _       = empty
+
+    noIdentifier :: (Alternative m) => Token -> String -> m (Token, String)
+    noIdentifier t [] = pure (t, [])
+    noIdentifier t s@(c:_)
+      | isIdentChar c = empty
+      | otherwise     = pure (t, s)
+
+    isIdentChar :: Char -> Bool
+    isIdentChar = liftM2 (||) isAlphaNum (== '_')