Data commit

Task/Commatizing-numbers/Haskell/commatizing-numbers.hs

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+#!/usr/bin/env runhaskell
+
+import Control.Monad (forM_)
+import Data.Char (isDigit)
+import Data.List (intercalate)
+import Data.Maybe (fromMaybe)
+
+{-
+I use the suffix "2" in identifiers in place of the more conventional
+prime (single quote character), because Rosetta Code's syntax highlighter
+still doesn't handle primes in identifiers correctly.
+-}
+
+isDigitOrPeriod :: Char -> Bool
+isDigitOrPeriod '.' = True
+isDigitOrPeriod c = isDigit c
+
+chopUp :: Int -> String -> [String]
+chopUp _ [] = []
+chopUp by str
+  | by < 1 = [str]              -- invalid argument, leave string unchanged
+  | otherwise = let (pfx, sfx) = splitAt by str
+                in pfx : chopUp by sfx
+
+addSeps :: String -> Char -> Int -> (String -> String) -> String
+addSeps str sep by rev =
+  let (leading, number) = span (== '0') str
+      number2 = rev $ intercalate [sep] $ chopUp by $ rev number
+  in leading ++ number2
+
+processNumber :: String -> Char -> Int -> String
+processNumber str sep by =
+  let (beforeDecimal, rest) = span isDigit str
+      (decimal, afterDecimal) = splitAt 1 rest
+      beforeDecimal2 = addSeps beforeDecimal sep by reverse
+      afterDecimal2 = addSeps afterDecimal sep by id
+  in beforeDecimal2 ++ decimal ++ afterDecimal2
+
+commatize2 :: String -> Char -> Int -> String
+commatize2 [] _ _ = []
+commatize2 str sep by =
+  let (pfx, sfx) = break isDigitOrPeriod str
+      (number, sfx2) = span isDigitOrPeriod sfx
+  in pfx ++ processNumber number sep by ++ sfx2
+
+commatize :: String -> Maybe Char -> Maybe Int -> String
+commatize str sep by = commatize2 str (fromMaybe ',' sep) (fromMaybe 3 by)
+
+input :: [(String, Maybe Char, Maybe Int)]
+input =
+  [ ("pi=3.14159265358979323846264338327950288419716939937510582097494459231", Just ' ', Just 5)
+  , ("The author has two Z$100000000000000 Zimbabwe notes (100 trillion).", Just '.', Nothing)
+  , ("\"-in Aus$+1411.8millions\"", Nothing, Nothing)
+  , ("===US$0017440 millions=== (in 2000 dollars)", Nothing, Nothing)
+  , ("123.e8000 is pretty big.", Nothing, Nothing)
+  , ("The land area of the earth is 57268900(29% of the surface) square miles.", Nothing, Nothing)
+  , ("Ain't no numbers in this here words, nohow, no way, Jose.", Nothing, Nothing)
+  , ("James was never known as 0000000007", Nothing, Nothing)
+  , ("Arthur Eddington wrote: I believe there are 15747724136275002577605653961181555468044717914527116709366231425076185631031296 protons in the universe.", Nothing, Nothing)
+  , ("   $-140000±100 millions.", Nothing, Nothing)
+  , ("6/9/1946 was a good year for some.", Nothing, Nothing)
+  ]
+
+main :: IO ()
+main =
+  forM_ input $ \(str, by, sep) -> do
+    putStrLn str
+    putStrLn $ commatize str by sep
+    putStrLn ""