Fix some wording in Calc and remove TODOs

TODO's shouldn't be visible in the finished book. Put as issues or
something instead.

Author: bryal

Physics/src/Calculus/FunExpr.lhs

@@ -33,7 +33,7 @@ which is really equivalent to
 
 $$D(x \mapsto x^2) = x \mapsto 2x$$
 
-or
+or with more descriptive function names
 
 $$D(square) = double$$.
 
@@ -136,12 +136,12 @@ left-associative, and set the precedence.
 > -- Medium precedence
 > infixl 6 :+
 > infixl 6 :-
-> -- Higher
+> -- High precedence
 > infixl 7 :*
 > infixl 7 :/
-> -- Higherer
+> -- Higher precedence
 > infixl 8 :^
-> -- High as a kite
+> -- Higherer precedence
 > infixl 9 :.
 
 
@@ -198,7 +198,7 @@ expressions in a much more human friendly way!
 < ghci> carPosition
 < (10 + ((50 + (20 * id)) * id))
 
-Still a bit noisy with all the parens, but much better!
+Still a bit noisy with all the parentheses, but much better!
 
 Another class we need to instance for our `FunExpr` is
 `Arbitrary`. This class is associated with the testing library

Physics/src/Calculus/Intro.lhs

@@ -3,10 +3,6 @@
 What is calculus?
 ======================================================================
 
-TODO: Proofs/tests/verification
-
-TODO: Have someone critique this
-
 Plain equations where all values are of the same dimension are all
 fine and well.  The importance of being able to solve basic problems
 like "If Jenny has 22 meters, and Richard has 18 meters: how many
@@ -20,8 +16,8 @@ more interesting problems like this, we need calculus.
 Calculus is the study of stuff that continuously change over time (or
 some other continuous variable). For example, a distance that changes
 over time is equivalent to a speed or a velocity, depending on how
-many dimensions you have, and a volume that changes as a length
-changes does not have a name, as far as I know.
+many dimensions you have. You can have rates of changes with respect
+to other units, like length, as well, but those are not as common.
 
 There are two major branches of calculus, differential calculus and
 integral calculus. Differential calculus is all about those rates of

Physics/src/Calculus/VisVerApp.lhs

@@ -4,7 +4,7 @@
 > 
 > import Hatlab.Plot
 
-Visualization with Hatlab
+Plotting with Hatlab
 --------------------------------------------------------------------
 
 The brain likes seeing things. Let's give it a good looking reward!
@@ -44,26 +44,3 @@ Then plot with
 Waddaya know! They look identical! I guess it just goes to
 show that a good approximation is often good enough.
 
-
-
-TODO: Verification
----------------------------------------------------------------------
-
-QuickCheck everything. Verify that simplified expressions evaluate to
-equivalent function as original
-
-
-
-
-TODO: Applying our DSL to solve physics problems!
-----------------------------------------------------------------------
-
-Mostly problems regarding position, velocity, acceleration, time.
-
-Average FOO vs. Instantaneous FOO -- Differences vs Derivatives.
-
-Integrating to get rid of /t:s.
-
-cool stuff here in general.
-
-Also, many pretty pictores

Physics/src/Introduction/Introduction.lhs

@@ -66,7 +66,9 @@ expressions for validity.
 Look, we'll demonstrate. Let's say we want to model a language that is
 a subset to the common algebra we're all familiar with. Our language
 will consist expressions of a single variable and addition. For
-example, these are valid expressions in such a language:
+example, the following three expressions are all valid in such a language:
+
+$$x + x$$
 
 $$x$$
 
@@ -90,7 +92,7 @@ or two expressions added together.
 
 And that's it, kind of! A DSL without any associated functions for
 validation, symbolic manipulation, evaluation, or somesuch, is really
-no DSL at all! We mush DO something with it, or there is no point!
+no DSL at all! We must DO something with it, or there is no point!
 
 One thing we can do with expressions such as these, is compare whether
 two of them are equal. Even without using any numbers, we can test