lab09: init

lab09/csvParserImproved.hs

@@ -0,0 +1,40 @@
+import Text.ParserCombinators.Parsec
+import System.Environment
+
+-- Each parser takes in a sequence of Chars and returns either
+--  * an array of Strings ([String])
+--  * an array of arrays of Strings ([String])
+
+csvFile :: GenParser Char st [[String]]
+csvFile = line `endBy` eol -- a series of lines ended by the end of the file
+
+line :: GenParser Char st [String]
+line = cell `sepBy` (char ',') -- a series of cells separated by commas
+
+cell :: GenParser Char st String
+cell = many (noneOf ",\n")
+
+eol :: GenParser Char st String
+{-
+eol = char '\n' -- does not work on Windows
+eol = string "\n" <|> string "\n\r" -- always matches first pattern
+eol = string "\n\r" <|> string "\n" -- fails on non-windows, since the left hand tries and consumes the \n
+eol = do -- works, but ugly, and changes the types
+  char '\n'
+  char '\r' <|> return '\n'
+-}
+eol = try (string "\n\r")
+       <|> string "\n"
+       <?> "end of line"
+
+
+parseCSV :: String -> Either ParseError [[String]]
+parseCSV input = parse csvFile "(unknown)" input
+
+main = do
+  args <- getArgs
+  p <- parseFromFile csvFile (head args)
+  case p of
+    Left err  -> print err
+    Right csv -> print csv
+