Some changes to the first three chapters.

000_introduction.md

@@ -199,10 +199,11 @@ large variety of program correctness properties.
 * Modeling and verifying theorems in mathematics and logic.
 * Preventing data races and deadlocks in concurrent systems.
 
-Type systems can never capture all possible behavior of the program. Although
-more sophisticated type systems are increasingly able to model a large space of
-behavior and is one of the most exciting areas of modern computer science
-research. Put most bluntly, **static types let you be dumb** and offload the
+Even though type systems will never be able to capture all aspects of a
+program, more sophisticated type systems are increasingly able to model a large
+space of program behavior.
+They are one of the most exciting areas of modern computer science research.
+Put most bluntly, **static types let you be dumb** and offload the
 checking that you would otherwise have to do in your head to a system that can
 do the reasoning for you and work with you to interactively build your program.
 

001_basics.md

@@ -758,7 +758,8 @@ context. The primary function ``tell`` adds a value to the writer context.
 tell :: (Monoid w) => w -> Writer w ()
 ```
 
-The monad can be devalued with or without the collected values.
+The monad can be evaluated returning the collected writer context and
+optionally the returned value.
 
 ```haskell
 execWriter :: (Monoid w) => Writer w a -> w

002_parsers.md

@@ -40,8 +40,9 @@ the AST.
 ~~~~ {.haskell slice="chapter3/parsec.hs" lower=8 upper=8}
 ~~~~
 
-Running the function will result in traversing the stream of characters yielding
-a resultant AST structure for the type variable ``a``, or failing with a parse
+Running the function will result in traversing the stream of characters
+yielding a value of type ``a`` that usually represents the AST for the
+parsed expression, or failing with a parse
 error for malformed input, or failing by not consuming the entire stream of
 input. A more robust implementation would track the position information of
 failures for error reporting.
@@ -70,7 +71,7 @@ it over the result of second parse function. Since the parser operation yields a
 list of tuples, composing a second parser function simply maps itself over the
 resulting list and concat's the resulting nested list of lists into a single
 flat list in the usual list monad fashion. The unit operation injects a single
-pure value into the parse stream.
+pure value as result without reading from the parse stream.
 
 ~~~~ {.haskell slice="chapter3/parsec.hs" lower=23 upper=28}
 ~~~~