add ex1 and ex2

exercise1/ex1.hs

+zipL :: ([Int],[Int]) -> [[Int]]
+zipL (xs,ys) | length xs /= length ys = [[]]
+zipL ([],[])     = []
+zipL (x:xs,y:ys) = [x,y] : zipL (xs,ys)
\ No newline at end of file

exercise2stack/.gitignore

+.stack-work/
+*~
\ No newline at end of file

exercise2stack/ChangeLog.md

+# Changelog for exercise2stack
+
+## Unreleased changes

exercise2stack/LICENSE

+Copyright ik (c) 2021
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of ik nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

exercise2stack/README.md

+# exercise2stack

exercise2stack/Setup.hs

+import Distribution.Simple
+main = defaultMain

exercise2stack/Sheet2/Task1/Main.hs

+import Tokens
+import System.Environment
+import Control.Exception
+import System.IO
+
+
+main :: IO ()
+main = catch main' noLex
+
+main' = do (fileName : _ ) <- getArgs 
+           sourceText <- readFile fileName
+           putStrLn ("Lexing : " ++ sourceText)
+           let lexedProg = alexScanTokens sourceText
+           putStrLn ("Lexed as " ++ (show lexedProg))
+
+noLex :: ErrorCall -> IO ()
+noLex e = do let err =  show e
+             hPutStr stderr ("Problem with Lexing : " ++ err)
+             return ()
\ No newline at end of file

exercise2stack/Sheet2/Task1/Tokens.x

+{ 
+module Tokens where 
+}
+
+%wrapper "basic" 
+$digit = 0-9     
+-- digits 
+$alpha = [a-zA-Z]    
+-- alphabetic characters
+
+tokens :-
+$white+       ; 
+  "--".*        ; 
+  let           { \s -> TokenLet } 
+  in            { \s -> TokenIn }
+  $digit+       { \s -> TokenInt (read s) } 
+  \=            { \s -> TokenEq }
+  \+            { \s -> TokenPlus }
+  \-            { \s -> TokenMinus }
+  \*            { \s -> TokenTimes }
+  \/            { \s -> TokenDiv }
+  \^            { \s -> TokenExp }
+  \(            { \s -> TokenLParen }
+  \)            { \s -> TokenRParen }
+  $alpha [$alpha $digit \_ \']*   { \s -> TokenVar s } 
+
+{ 
+-- Each action has type :: String -> Token 
+-- The token type: 
+data Token = 
+  TokenLet         | 
+  TokenIn          | 
+  TokenInt Int     |
+  TokenVar String  | 
+  TokenEq          |
+  TokenPlus        |
+  TokenMinus       |
+  TokenTimes       |
+  TokenDiv         |
+  TokenExp         |
+  TokenLParen      |
+  TokenRParen       
+  deriving (Eq,Show) 
+
+}
\ No newline at end of file

exercise2stack/Sheet2/Task2/Main.hs

+import Tokens
+import System.Environment
+import Control.Exception
+import System.IO
+
+
+main :: IO ()
+main = catch main' noLex
+
+main'  = do (fileName : _ ) <- getArgs 
+            sourceText <- readFile fileName
+            putStrLn ("Lexing : " ++ sourceText)
+            let lexedProg = (alexScanTokens sourceText)
+            putStrLn ("lexed as " ++ (show lexedProg))
+
+noLex :: ErrorCall -> IO ()
+noLex e = do let err =  show e
+             hPutStr stderr ("Problem with lexing: " ++ err)
+             return ()
\ No newline at end of file

exercise2stack/Sheet2/Task2/Tokens.x

+{ 
+module Tokens where 
+}
+
+%wrapper "posn" 
+$digit = 0-9     
+-- digits 
+$alpha = [a-zA-Z]    
+-- alphabetic characters
+
+tokens :-
+  $white+       ; 
+  "--".*        ; 
+  let           { \p s -> TokenLet p} 
+  in            { \p s -> TokenIn p }
+  $digit+       { \p s -> TokenInt p (read s) } 
+  \=            { \p s -> TokenEq p }
+  \+            { \p s -> TokenPlus p }
+  \-            { \p s -> TokenMinus p }
+  \*            { \p s -> TokenTimes p }
+  \/            { \p s -> TokenDiv p }
+  \^            { \p s -> TokenExp p }
+  \(            { \p s -> TokenLParen p }
+  \)            { \p s -> TokenRParen p }
+  $alpha [$alpha $digit \_ \’]*   { \p s -> TokenVar p s } 
+
+{ 
+-- Each action has type :: AlexPosn -> String -> Token 
+
+-- The token type: 
+data Token = 
+  TokenLet AlexPosn        | 
+  TokenIn  AlexPosn        | 
+  TokenInt AlexPosn Int    |
+  TokenVar AlexPosn String | 
+  TokenEq  AlexPosn        |
+  TokenPlus AlexPosn       |
+  TokenMinus AlexPosn      |
+  TokenTimes AlexPosn      |
+  TokenDiv AlexPosn        |
+  TokenExp AlexPosn        |
+  TokenLParen AlexPosn     |
+  TokenRParen AlexPosn      
+  deriving (Eq,Show) 
+
+tokenPosn :: Token -> String
+tokenPosn (TokenInt  (AlexPn a l c) n) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenVar  (AlexPn a l c) x) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenLet (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenIn  (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenEq  (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenPlus (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenMinus (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenTimes (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenDiv (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenExp (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenLParen (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenRParen (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+
+
+}
\ No newline at end of file

exercise2stack/Sheet2/Task3/MDLTokens.x

+{ 
+module MDLTokens where 
+}
+
+%wrapper "posn" 
+$digit = 0-9     
+-- digits 
+
+tokens :-
+$white+       ; 
+  "--".*        ; 
+  Forward        { (\p s -> TokenForward p)} 
+  Rotate         { (\p s -> TokenRotate p) }
+  [1-9]          { (\p s -> TokenDigit p (read s)) } 
+  $digit $digit+ { (\p s -> TokenInt p (read s)) }
+  Check          { (\p s -> TokenCheck p) }
+  If             { (\p s -> TokenIf p) }
+  Then           { (\p s -> TokenThen p) }
+  Else           { (\p s -> TokenElse p) }
+  L              { (\p s -> TokenLeft p) }
+  R              { (\p s -> TokenRight p) }
+  \;             { (\p s -> TokenSeq p )}
+  \(             { (\p s -> TokenLParen p) }
+  \)             { (\p s -> TokenRParen p) }
+
+{ 
+-- Each action has type :: AlexPosn -> String -> MDLToken 
+
+-- The token type: 
+data MDLToken = 
+  TokenForward AlexPosn        | 
+  TokenRotate  AlexPosn        | 
+  TokenDigit AlexPosn Int      |
+  TokenInt AlexPosn Int        | 
+  TokenCheck AlexPosn          |
+  TokenIf AlexPosn             |
+  TokenThen AlexPosn           |
+  TokenElse AlexPosn           |
+  TokenLeft AlexPosn           |
+  TokenRight AlexPosn          |
+  TokenSeq AlexPosn            |
+  TokenLParen AlexPosn         |
+  TokenRParen AlexPosn      
+  deriving (Eq,Show) 
+
+tokenPosn :: MDLToken -> String
+tokenPosn (TokenForward (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenRotate  (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenDigit  (AlexPn a l c) _) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenInt  (AlexPn a l c) _) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenCheck  (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenIf (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenThen (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenElse (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenLeft (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenRight (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenSeq (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenLParen (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+tokenPosn (TokenRParen (AlexPn a l c)) = show(l) ++ ":" ++ show(c)
+
+
+}
\ No newline at end of file

exercise2stack/Sheet2/Task3/Main.hs

+import MDLTokens
+import System.Environment
+import Control.Exception
+import System.IO
+
+
+main :: IO ()
+main = catch main' noParse
+
+main' = do (fileName : _ ) <- getArgs 
+           sourceText <- readFile fileName
+           putStrLn ("Parsing : " ++ sourceText)
+           let parsedProg = parseCalc (alexScanTokens sourceText)
+           putStrLn ("Parsed as " ++ (show parsedProg))
+
+noParse :: ErrorCall -> IO ()
+noParse e = do let err =  show e
+               hPutStr stderr err
+               return ()
\ No newline at end of file

exercise2stack/Sheet2/Task3/example.mdl

+Forward 10 ; 
+Rotate L ;
+If (Check 3) 
+ Then Rotate L ; Forward 1 ; Rotate R
+ Else Forward 3 ; Rotate L

exercise2stack/Sheet2/Task3/exampleErr.mdl

+Forward 10 ; 
+Rotate L ;
+If (Check 3) 
+ Then Rotate L ; Forward 1 ; Rotate R
+ Else Forward 3 ; Rotate L
+Rotate L

exercise2stack/app/Main.hs

+module Main where
+
+import Tokens
+import System.Environment
+import Control.Exception
+import System.IO
+
+main :: IO ()
+main = catch main' noLex
+
+main' = do (fileName : _) <- getArgs
+           sourceText <- readFile fileName
+           putStrLn $ "Lexing: " ++ sourceText
+           let lexedProg = alexScanTokens sourceText
+           putStrLn $ "Lexed as: " ++ (show lexedProg)
+
+noLex :: ErrorCall -> IO ()
+noLex e = do let err = show e
+             hPutStrLn stderr ("Problem with lexing :" ++ err)
+             return ()
\ No newline at end of file

exercise2stack/app/Tokens.hs

+{-# OPTIONS_GHC -fno-warn-unused-binds -fno-warn-missing-signatures #-}
+{-# LANGUAGE CPP #-}
+{-# LINE 1 "Tokens.x" #-}
+ 
+module Tokens where 
+
+#if __GLASGOW_HASKELL__ >= 603
+#include "ghcconfig.h"
+#elif defined(__GLASGOW_HASKELL__)
+#include "config.h"
+#endif
+#if __GLASGOW_HASKELL__ >= 503
+import Data.Array
+#else
+import Array
+#endif
+{-# LINE 1 "templates/wrappers.hs" #-}
+-- -----------------------------------------------------------------------------
+-- Alex wrapper code.
+--
+-- This code is in the PUBLIC DOMAIN; you may copy it freely and use
+-- it for any purpose whatsoever.
+
+
+
+
+
+import Data.Word (Word8)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+import Data.Char (ord)
+import qualified Data.Bits
+
+-- | Encode a Haskell String to a list of Word8 values, in UTF8 format.
+utf8Encode :: Char -> [Word8]
+utf8Encode = uncurry (:) . utf8Encode'
+
+utf8Encode' :: Char -> (Word8, [Word8])
+utf8Encode' c = case go (ord c) of
+                  (x, xs) -> (fromIntegral x, map fromIntegral xs)
+ where
+  go oc
+   | oc <= 0x7f       = ( oc
+                        , [
+                        ])
+
+   | oc <= 0x7ff      = ( 0xc0 + (oc `Data.Bits.shiftR` 6)
+                        , [0x80 + oc Data.Bits..&. 0x3f
+                        ])
+
+   | oc <= 0xffff     = ( 0xe0 + (oc `Data.Bits.shiftR` 12)
+                        , [0x80 + ((oc `Data.Bits.shiftR` 6) Data.Bits..&. 0x3f)
+                        , 0x80 + oc Data.Bits..&. 0x3f
+                        ])
+   | otherwise        = ( 0xf0 + (oc `Data.Bits.shiftR` 18)
+                        , [0x80 + ((oc `Data.Bits.shiftR` 12) Data.Bits..&. 0x3f)
+                        , 0x80 + ((oc `Data.Bits.shiftR` 6) Data.Bits..&. 0x3f)
+                        , 0x80 + oc Data.Bits..&. 0x3f
+                        ])
+
+
+
+type Byte = Word8
+
+-- -----------------------------------------------------------------------------
+-- The input type
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+-- -----------------------------------------------------------------------------
+-- Token positions
+
+-- `Posn' records the location of a token in the input text.  It has three
+-- fields: the address (number of chacaters preceding the token), line number
+-- and column of a token within the file. `start_pos' gives the position of the
+-- start of the file and `eof_pos' a standard encoding for the end of file.
+-- `move_pos' calculates the new position after traversing a given character,
+-- assuming the usual eight character tab stops.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+-- -----------------------------------------------------------------------------
+-- Monad (default and with ByteString input)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+-- -----------------------------------------------------------------------------
+-- Basic wrapper
+
+
+type AlexInput = (Char,[Byte],String)
+
+alexInputPrevChar :: AlexInput -> Char
+alexInputPrevChar (c,_,_) = c
+
+-- alexScanTokens :: String -> [token]
+alexScanTokens str = go ('\n',[],str)
+  where go inp__@(_,_bs,s) =
+          case alexScan inp__ 0 of
+                AlexEOF -> []
+                AlexError _ -> error "lexical error"
+                AlexSkip  inp__' _ln     -> go inp__'
+                AlexToken inp__' len act -> act (take len s) : go inp__'
+
+alexGetByte :: AlexInput -> Maybe (Byte,AlexInput)
+alexGetByte (c,(b:bs),s) = Just (b,(c,bs,s))
+alexGetByte (_,[],[])    = Nothing
+alexGetByte (_,[],(c:s)) = case utf8Encode' c of
+                             (b, bs) -> Just (b, (c, bs, s))
+
+
+
+-- -----------------------------------------------------------------------------
+-- Basic wrapper, ByteString version
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+-- -----------------------------------------------------------------------------
+-- Posn wrapper
+
+-- Adds text positions to the basic model.
+
+
+
+
+
+
+
+
+
+
+
+
+
+-- -----------------------------------------------------------------------------
+-- Posn wrapper, ByteString version
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+-- -----------------------------------------------------------------------------
+-- GScan wrapper
+
+-- For compatibility with previous versions of Alex, and because we can.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+alex_tab_size :: Int
+alex_tab_size = 8
+alex_base :: Array Int Int
+alex_base = listArray (0 :: Int, 28)
+  [ -8
+  , -147
+  , -76
+  , 0
+  , 37
+  , 0
+  , 165
+  , -121
+  , 293
+  , 549
+  , 485
+  , 0
+  , -1
+  , 731
+  , 939
+  , 1014
+  , -35
+  , 0
+  , 0
+  , -22
+  , 0
+  , 0
+  , 0
+  , 0
+  , 0
+  , 1101
+  , 1176
+  , 1263
+  , 1338
+  ]
+
+alex_table :: Array Int Int
+alex_table = listArray (0 :: Int, 1593)
+  [ 0
+  , 12
+  , 12
+  , 12
+  , 12
+  , 12
+  , 26
+  , 1
+  , 12
+  , 12
+  , 12
+  , 12
+  , 12
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 13
+  , 12
+  , 0
+  , 0
+  , 0
+  , 0
+  , 0
+  , 0
+  , 12
+  , 22
+  , 23
+  , 20
+  , 18
+  , 0
+  , 19
+  , 0
+  , 21
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 16
+  , 0
+  , 0
+  , 0
+  , 17
+  , 0
+  , 0
+  , 0
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 0
+  , 0
+  , 0
+  , 24
+  , 0
+  , 0
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 27
+  , 26
+  , 26
+  , 25
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 26
+  , 10
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , 2
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
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+
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+  , -1
+  , -1
+  , -1
+  , -1
+  , 48
+  , 49
+  , 50
+  , 51
+  , 52
+  , 53
+  , 54
+  , 55
+  , 56
+  , 57
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , 226
+  , 65
+  , 66
+  , 67
+  , 68
+  , 69
+  , 70
+  , 71
+  , 72
+  , 73
+  , 74
+  , 75
+  , 76
+  , 77
+  , 78
+  , 79
+  , 80
+  , 81
+  , 82
+  , 83
+  , 84
+  , 85
+  , 86
+  , 87
+  , 88
+  , 89
+  , 90
+  , -1
+  , -1
+  , -1
+  , -1
+  , 95
+  , -1
+  , 97
+  , 98
+  , 99
+  , 100
+  , 101
+  , 102
+  , 103
+  , 104
+  , 105
+  , 106
+  , 107
+  , 108
+  , 109
+  , 110
+  , 111
+  , 112
+  , 113
+  , 114
+  , 115
+  , 116
+  , 117
+  , 118
+  , 119
+  , 120
+  , 121
+  , 122
+  , 48
+  , 49
+  , 50
+  , 51
+  , 52
+  , 53
+  , 54
+  , 55
+  , 56
+  , 57
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , 226
+  , 65
+  , 66
+  , 67
+  , 68
+  , 69
+  , 70
+  , 71
+  , 72
+  , 73
+  , 74
+  , 75
+  , 76
+  , 77
+  , 78
+  , 79
+  , 80
+  , 81
+  , 82
+  , 83
+  , 84
+  , 85
+  , 86
+  , 87
+  , 88
+  , 89
+  , 90
+  , -1
+  , -1
+  , -1
+  , -1
+  , 95
+  , -1
+  , 97
+  , 98
+  , 99
+  , 100
+  , 101
+  , 102
+  , 103
+  , 104
+  , 105
+  , 106
+  , 107
+  , 108
+  , 109
+  , 110
+  , 111
+  , 112
+  , 113
+  , 114
+  , 115
+  , 116
+  , 117
+  , 118
+  , 119
+  , 120
+  , 121
+  , 122
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , 226
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , 226
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  ]
+
+alex_deflt :: Array Int Int
+alex_deflt = listArray (0 :: Int, 28)
+  [ -1
+  , -1
+  , 11
+  , 11
+  , 3
+  , 3
+  , -1
+  , -1
+  , -1
+  , 13
+  , 13
+  , 13
+  , -1
+  , 13
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  , -1
+  ]
+
+alex_accept = listArray (0 :: Int, 28)
+  [ AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccNone
+  , AlexAccSkip
+  , AlexAccSkip
+  , AlexAcc 14
+  , AlexAcc 13
+  , AlexAcc 12
+  , AlexAcc 11
+  , AlexAcc 10
+  , AlexAcc 9
+  , AlexAcc 8
+  , AlexAcc 7
+  , AlexAcc 6
+  , AlexAcc 5
+  , AlexAcc 4
+  , AlexAcc 3
+  , AlexAcc 2
+  , AlexAcc 1
+  , AlexAcc 0
+  ]
+
+alex_actions = array (0 :: Int, 15)
+  [ (14,alex_action_2)
+  , (13,alex_action_3)
+  , (12,alex_action_4)
+  , (11,alex_action_5)
+  , (10,alex_action_6)
+  , (9,alex_action_7)
+  , (8,alex_action_8)
+  , (7,alex_action_9)
+  , (6,alex_action_10)
+  , (5,alex_action_11)
+  , (4,alex_action_12)
+  , (3,alex_action_13)
+  , (2,alex_action_13)
+  , (1,alex_action_13)
+  , (0,alex_action_13)
+  ]
+
+{-# LINE 27 "Tokens.x" #-}
+ 
+-- Each action has type :: String -> Token 
+-- The token type: 
+data Token = 
+  TokenLet         | 
+  TokenIn          | 
+  TokenInt Int     |
+  TokenVar String  | 
+  TokenEq          |
+  TokenPlus        |
+  TokenMinus       |
+  TokenTimes       |
+  TokenDiv         |
+  TokenExp         |
+  TokenLParen      |
+  TokenRParen       
+  deriving (Eq,Show) 
+
+
+alex_action_2 =  \s -> TokenLet 
+alex_action_3 =  \s -> TokenIn 
+alex_action_4 =  \s -> TokenInt (read s) 
+alex_action_5 =  \s -> TokenEq 
+alex_action_6 =  \s -> TokenPlus 
+alex_action_7 =  \s -> TokenMinus 
+alex_action_8 =  \s -> TokenTimes 
+alex_action_9 =  \s -> TokenDiv 
+alex_action_10 =  \s -> TokenLParen 
+alex_action_11 =  \s -> TokenRParen 
+alex_action_12 =  \s -> TokenExp
+alex_action_13 =  \s -> TokenVar s 
+{-# LINE 1 "templates/GenericTemplate.hs" #-}
+-- -----------------------------------------------------------------------------
+-- ALEX TEMPLATE
+--
+-- This code is in the PUBLIC DOMAIN; you may copy it freely and use
+-- it for any purpose whatsoever.
+
+-- -----------------------------------------------------------------------------
+-- INTERNALS and main scanner engine
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+alexIndexInt16OffAddr arr off = arr ! off
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+alexIndexInt32OffAddr arr off = arr ! off
+
+
+
+
+
+
+
+
+
+
+
+quickIndex arr i = arr ! i
+
+
+-- -----------------------------------------------------------------------------
+-- Main lexing routines
+
+data AlexReturn a
+  = AlexEOF
+  | AlexError  !AlexInput
+  | AlexSkip   !AlexInput !Int
+  | AlexToken  !AlexInput !Int a
+
+-- alexScan :: AlexInput -> StartCode -> AlexReturn a
+alexScan input__ (sc)
+  = alexScanUser undefined input__ (sc)
+
+alexScanUser user__ input__ (sc)
+  = case alex_scan_tkn user__ input__ (0) input__ sc AlexNone of
+  (AlexNone, input__') ->
+    case alexGetByte input__ of
+      Nothing ->
+
+
+
+                                   AlexEOF
+      Just _ ->
+
+
+
+                                   AlexError input__'
+
+  (AlexLastSkip input__'' len, _) ->
+
+
+
+    AlexSkip input__'' len
+
+  (AlexLastAcc k input__''' len, _) ->
+
+
+
+    AlexToken input__''' len (alex_actions ! k)
+
+
+-- Push the input through the DFA, remembering the most recent accepting
+-- state it encountered.
+
+alex_scan_tkn user__ orig_input len input__ s last_acc =
+  input__ `seq` -- strict in the input
+  let
+  new_acc = (check_accs (alex_accept `quickIndex` (s)))
+  in
+  new_acc `seq`
+  case alexGetByte input__ of
+     Nothing -> (new_acc, input__)
+     Just (c, new_input) ->
+
+
+
+      case fromIntegral c of { (ord_c) ->
+        let
+                base   = alexIndexInt32OffAddr alex_base s
+                offset = (base + ord_c)
+                check  = alexIndexInt16OffAddr alex_check offset
+
+                new_s = if (offset >= (0)) && (check == ord_c)
+                          then alexIndexInt16OffAddr alex_table offset
+                          else alexIndexInt16OffAddr alex_deflt s
+        in
+        case new_s of
+            (-1) -> (new_acc, input__)
+                -- on an error, we want to keep the input *before* the
+                -- character that failed, not after.
+            _ -> alex_scan_tkn user__ orig_input (if c < 0x80 || c >= 0xC0 then (len + (1)) else len)
+                                                -- note that the length is increased ONLY if this is the 1st byte in a char encoding)
+                        new_input new_s new_acc
+      }
+  where
+        check_accs (AlexAccNone) = last_acc
+        check_accs (AlexAcc a  ) = AlexLastAcc a input__ (len)
+        check_accs (AlexAccSkip) = AlexLastSkip  input__ (len)
+
+        check_accs (AlexAccPred a predx rest)
+           | predx user__ orig_input (len) input__
+           = AlexLastAcc a input__ (len)
+           | otherwise
+           = check_accs rest
+        check_accs (AlexAccSkipPred predx rest)
+           | predx user__ orig_input (len) input__
+           = AlexLastSkip input__ (len)
+           | otherwise
+           = check_accs rest
+
+
+data AlexLastAcc
+  = AlexNone
+  | AlexLastAcc !Int !AlexInput !Int
+  | AlexLastSkip     !AlexInput !Int
+
+data AlexAcc user
+  = AlexAccNone
+  | AlexAcc Int
+  | AlexAccSkip
+
+  | AlexAccPred Int (AlexAccPred user) (AlexAcc user)
+  | AlexAccSkipPred (AlexAccPred user) (AlexAcc user)
+
+type AlexAccPred user = user -> AlexInput -> Int -> AlexInput -> Bool
+
+-- -----------------------------------------------------------------------------
+-- Predicates on a rule
+
+alexAndPred p1 p2 user__ in1 len in2
+  = p1 user__ in1 len in2 && p2 user__ in1 len in2
+
+--alexPrevCharIsPred :: Char -> AlexAccPred _
+alexPrevCharIs c _ input__ _ _ = c == alexInputPrevChar input__
+
+alexPrevCharMatches f _ input__ _ _ = f (alexInputPrevChar input__)
+
+--alexPrevCharIsOneOfPred :: Array Char Bool -> AlexAccPred _
+alexPrevCharIsOneOf arr _ input__ _ _ = arr ! alexInputPrevChar input__
+
+--alexRightContext :: Int -> AlexAccPred _
+alexRightContext (sc) user__ _ _ input__ =
+     case alex_scan_tkn user__ input__ (0) input__ sc AlexNone of
+          (AlexNone, _) -> False
+          _ -> True
+        -- TODO: there's no need to find the longest
+        -- match when checking the right context, just
+        -- the first match will do.
+