lab09: init

lab09/complex.json

@@ -0,0 +1,11 @@
+{
+  name: "Complex number list example",
+  nums: [
+    { real: 42, imaginary: 1 },
+    { real: 30, imaginary: 0 },
+    { real: 15, imaginary: 7 }
+  ],
+  knownIssues: null,
+  verified: false
+}
+  

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
+

lab09/csvParserImproved.hs

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+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
+

lab09/jsonParser.hs

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+import Text.ParserCombinators.Parsec
+import System.Environment
+
+data JValue = JString String
+            | JNumber Double
+            | JBool Bool
+            | JNull
+            | JObject [(String, JValue)]
+            | JArray [JValue]
+  deriving (Eq, Ord, Show)
+
+
+jsonFile :: GenParser Char st JValue
+jsonFile = do
+  result <- jsonArr
+  spaces
+  eof
+  return result
+
+jsonElem :: GenParser Char st JValue
+jsonElem = do
+  spaces
+  result <- jsonElem'
+  spaces
+  return result
+
+jsonElem' = jsonArr
+        <|> jsonString
+        <|> jsonBool
+        <|> jsonNull
+        <?> "json element"
+
+jsonString :: GenParser Char st JValue
+jsonString = jsonStringDQ <|> jsonStringSQ
+
+jsonStringDQ = do
+  char '"'
+  s <- many $ noneOf "\"" -- crude.  does not allow double quotes within strings
+  char '"'
+  return $ JString s
+
+jsonStringSQ = do
+  char '\''
+  s <- many $ noneOf "'" -- crude, same as above
+  char '\''
+  return $ JString s
+
+jsonBool = do
+  bStr <- string "true" <|> string "false"
+  return $ case bStr of
+    "true" -> JBool True
+    "false" -> JBool False
+
+jsonNull = do
+  string "null"
+  return JNull
+
+jsonArr = do
+  char '['
+  arr <- jsonElem `sepBy` (char ',')
+  char ']'
+  return $ JArray arr
+
+
+
+parseJSON :: String -> Either ParseError JValue
+parseJSON input = parse jsonFile "(unknown)" input
+
+main = do
+  args <- getArgs
+  p <- parseFromFile jsonFile (head args)
+  case p of
+    Left err  -> print err
+    Right json -> print json
+
+

lab09/numList.json

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+[
+  42, 
+  33,
+  71
+]

lab09/strList.json

@@ -0,0 +1 @@
+['hi',"how",'are','u',null]

lab09/test.csv

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+Year,Make,Model,Length
+1997,Ford,E350,2.34
+2000,Mercury,Cougar,2.38
+