chatper 24 - completed the learning parsers exercises

Author: mukeshsoni

chapter24/learning-parsers/learning-parsers.cabal

@@ -18,4 +18,5 @@ executable learning-parsers
   main-is:             Main.hs
   default-language:    Haskell2010
   build-depends:       base >= 4.7 && < 5
-                     , trifecta
+                     , trifecta
+                     , parsers

chapter24/learning-parsers/src/Main.hs

@@ -1,12 +1,15 @@
 module Main where
 
 import Text.Trifecta
+import Text.Parser.Combinators
 
 stop :: Parser a
 stop = unexpected "stop"
 
 one :: Parser Char
 one = char '1'
+two = char '2'
+three = char '3'
 
 one' = one >> stop
 
@@ -19,6 +22,26 @@ testParse :: Parser Char -> IO ()
 testParse p =
   print $ parseString p mempty "123"
 
+testEOF :: Parser () -> IO ()
+testEOF p =
+  print $ parseString p mempty "123"
+
+testString' :: Parser String -> IO ()
+testString' p =
+  print $ parseString p mempty "123"
+
+oneString :: Parser String
+oneString = string "1"
+
+oneTwoString :: Parser String
+oneTwoString = string "12"
+
+oneTwoThreeString :: Parser String
+oneTwoThreeString = string "123"
+
+-- oneTwoThreeString' :: Parser String
+-- oneTwoThreeString' = string "123" <|> string "12" <|> string "1"
+
 pNL s =
   putStrLn ('\n' : s)
 
@@ -34,4 +57,15 @@ main = do
   testParse oneTwo
   pNL "oneTwo':"
   testParse oneTwo'
-
+  pNL "oneTwoStop:"
+  testEOF (oneTwo >> eof)
+  pNL "oneString"
+  testString' oneString
+  pNL "oneTwoString"
+  testString' oneTwoString
+  pNL "oneTwoThreeString"
+  testString' oneTwoThreeString
+  pNL "oneTwoThreeString'"
+  testString' $ choice [oneTwoThreeString, oneTwoString, oneString]
+  pNL "oneTwoThreeChar'"
+  testString' $ choice [one >> two >> three, one >> two, one]