lab09: init

lab09/csvParser.hs

@@ -0,0 +1,46 @@
+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]]
+-- A csv file contains 0 or more lines and is terminated by the end of the file
+csvFile = do
+  result <- many line -- The result is an array of an array of Strings, i.e. [[String]]
+  eof -- match end of file
+  return result
+
+line :: GenParser Char st [String]
+-- A line is a comma separated list of values, ending with a newline character
+line = do
+  result <- cells
+  char '\n'  -- end of line, only works in Linux or OSX formatted files
+  return result
+
+cells :: GenParser Char st [String]
+cells = do
+  first <- cellContent
+  next <- remainingCells
+  return (first : next)
+
+remainingCells :: GenParser Char st [String]
+remainingCells = do
+  (char ',' >> cells) -- found a comma, so more cells
+  <|> (return []) -- No comma, so we wrap up an empty array
+
+cellContent :: GenParser Char st String
+cellContent =
+  many (noneOf ",\n") -- Matches any character that is not a comma or newline
+
+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
+