diff --git a/Hascal.hs b/Hascal.hs --- a/Hascal.hs +++ b/Hascal.hs @@ -3,7 +3,7 @@ -- -- Also, its source code is a nice example for a minimalistic Haskell project. -- --- Some examples for the usage of the command-line program: +-- Some examples for the usage of the command-line program (using bash): -- -- >>> hascal 1+2 -- 3.0 @@ -17,7 +17,7 @@ -- >>> hascal _1 ^ 0.5 -- !1.0 -- --- And as you can see, negative numbers are preceded by a underscore. +-- And as you can see, negative numbers are preceded by an underscore. -- -- Although hascal itself doesn't understand brackets, you can use your shell -- to get that functionality, like this (using bash): @@ -26,7 +26,7 @@ -- -1.0 -- -- Speaking of shells, you should consider that your shell might extend an --- asterisk (*) to the files at the current directory, like here: +-- asterisk (*) to the files at the current directory, like this: -- -- >>> echo * -- _darcs dist hascal.cabal Hascal.hs LICENSE Main.hs README.org Setup.hs @@ -41,7 +41,12 @@ -- >>> hascal 1*2 -- 2 -- --- Yeah, that's it. Hascal is really minimalistic. +-- Or, you could do: +-- +-- >>> hascal '1*2' +-- 2 +-- +-- Yeah, that's pretty much it. Hascal is really minimalistic. -- And I'm not planning to extend it much. module Hascal ( -- * Operators @@ -63,8 +68,7 @@ -- |'operators' is the default list of operators. -- --- An operator consists of one character and a function with of type --- @Number -> Number -> Number@. +-- An operator consists of one character and a function. -- -- 'operators' includes: -- @@ -99,13 +103,19 @@ calc :: (Read t, RealFloat t) => [(Char, Complex t -> Complex t -> Complex t)] -> String - -> Maybe (Complex t) -calc [] a = readNumber a -calc l@((c,f):s) a | z /= "" = case (calc l y,calc l z) of - (Just n,Just m) -> Just (f m n) - _ -> Nothing - | otherwise = calc s a - where (y,z) = second (drop 1) $ break (==c) a + -> Either String (Complex t) +calc [] a + = readNumber a +calc l@((c,f):s) a + | z /= "" + = case (calc l y,calc l z) of + (Right n,Right m) -> Right (f m n) + (Left n,_ ) -> Left n + (_ ,Left m) -> Left m + | otherwise + = calc s a + where + (y,z) = second (drop 1) $ break (==c) a -- |'eval' gets a list of operators and a string containing a mathematical @@ -114,36 +124,45 @@ eval :: (Read t, RealFloat t) => [(Char, Complex t -> Complex t -> Complex t)] -- ^ list of operators -> String -- ^ string containing term - -> Maybe (Complex t) -- ^ just result, or nothing + -> Either String (Complex t) -- ^ just result, or nothing eval = (. reverse) . calc -readNumber :: (Read t, RealFloat t) => String -> Maybe (Complex t) -readNumber ('!':s) = ((0:+1)*) <$> findOrRead s -readNumber ('_':s) = negate <$> findOrRead s -readNumber s = findOrRead s +-- Respects preceding exclamation marks and underscores before a number +readNumber :: (Read t, RealFloat t) => String -> Either String (Complex t) +readNumber x = case reverse x of + ('!':s) -> ((0:+1)*) <$> findOrRead s + ('_':s) -> negate <$> findOrRead s + ('-':s) -> Left ("Error at \"-" ++ + s ++ + "\".\n\nTo denote negative numbers, " ++ + "use a preceding underscore instead.") + s -> findOrRead s -findOrRead :: (Read t, Floating t) => String -> Maybe (Complex t) -findOrRead a = let s = reverse a in - maybe (maybeRead s) (Just . snd) $ find ((==s) . fst) +-- Checks whether the string is readable as a mathematical constant before +-- trying to read it as a number +findOrRead :: (Read t, Floating t) => String -> Either String (Complex t) +findOrRead s = maybe (maybeRead s) (Right . snd) $ find ((==s) . fst) [("pi",pi :+0) ,("e" ,exp 1:+0) ,("i" ,0 :+1) ] -maybeRead :: (Read t, Num t) => String -> Maybe (Complex t) -maybeRead s | any (null . snd) (reads s :: [(Double,String)]) - = Just (read s:+0) - | otherwise - = Nothing +-- Reads numbers +maybeRead :: (Read t, Num t) => String -> Either String (Complex t) +maybeRead s + | any (null . snd) (reads s :: [(Double,String)]) + = Right (read s:+0) + | otherwise + = Left ("Error at \"" ++ s ++ "\".") -- |'hascal' is the default evaluator: -- -- @ hascal = 'eval' 'operators' @ -hascal :: (Read t, RealFloat t) => String -> Maybe (Complex t) +hascal :: (Read t, RealFloat t) => String -> Either String (Complex t) hascal = eval operators @@ -151,5 +170,5 @@ -- E.g., it doesn't show the real or imaginary part of the number if it's @0@. prettyPrint :: (Show t, RealFloat t) => Complex t -> String prettyPrint (r:+0) = show r -prettyPrint (0:+i) = '!' : show i -prettyPrint (r:+i) = show r ++ " + !" ++ show i +prettyPrint (0:+i) = show i ++ "*i" +prettyPrint (r:+i) = show r ++ " + " ++ show i ++ "*i" diff --git a/Main.hs b/Main.hs --- a/Main.hs +++ b/Main.hs @@ -9,6 +9,10 @@ main :: IO () -main = getArgs >>= liftM2 unless null - (putStrLn . maybe "Error. :(" prettyPrint . - (hascal :: String -> Maybe (Complex CReal)) . concat) +main = do + args <- getArgs + unless (null args) $ + putStrLn $ + either id prettyPrint $ + (hascal :: String -> Either String (Complex CReal)) $ + concat args diff --git a/hascal.cabal b/hascal.cabal --- a/hascal.cabal +++ b/hascal.cabal @@ -1,10 +1,16 @@ name: hascal -version: 1.4.1 +version: 1.4.2 synopsis: A minimalistic but extensible and precise calculator -description: Hascal is a minimalistic calculator with infix-operations - supporting addition, subtraction, division, multiplication, - exponentiation and logarithming. - Futhermore, it's easy to add custom operators. +description: Hascal is both a simple but extendable calculator library for + Haskell as well as a command-line program using this library. + . + Hascal supports addition, subtraction, multiplication, division, + exponentiation, and logarithm, while it's easy to add custom + operators. + . + Hascal also supports complex numbers. Hascal can work at an + arbitrary precision. However, Hascal does not support + parenthesis. stability: provisional category: Math, Console, Tools, Utility, Utils, Parsing homepage: http://darcsden.com/mekeor/hascal @@ -26,7 +32,7 @@ source-repository head type: git - location: git://github.com/MekeorMelire/hascal.git + location: git://github.com/mekeor/hascal.git test-suite test