read-class.md

@@ -32,17 +32,19 @@
 
   GHC has used a new `Read` class based on these parsers since 5.04 (July 2002).
 
-- Malcolm's experimental [ Poly parser](http://nhc98.blogspot.com/#113301726218243351) in the development version of [ HaXml](http://www.cs.york.ac.uk/fp/HaXml-1.14/).
+- Malcolm's experimental [ Poly TextParser](http://nhc98.blogspot.com/#113301726218243351) in the development version of [ HaXml](http://www.cs.york.ac.uk/fp/HaXml-1.14/).
 
   - monadic interface, invoked with
 
     ```wiki
-    runParser :: Parser t a -> [t] -> (Either String a, [t])
+    runParser :: TextParser a -> String -> (Either String a, String)
     ```
 
-    (This is essentially the internal representation.)
-  - choice operator commits to the first successful alternative
+    (The internal representation is more general, parameterised on token type.)
+  - returns only the first successful alternative, but with internal backtracking,
+    and an explicit commit operator to prevent backtracking where necessary
   - on failure, returns an error string and the unparsed input
+  - failure messages can be defined/combined/nested with convenient combinators
 
 - Could also use something based on Daan's [ Parsec](http://www.cs.uu.nl/people/daan/parsec.html) combinators