Merge remote-tracking branch 'adambard/master'

1 files changed, 23 insertions, 24 deletions

diff --git a/haskell.html.markdown b/haskell.html.markdown
index 200e2538..4e254070 100644
--- a/haskell.html.markdown
+++ b/haskell.html.markdown
@@ -64,11 +64,11 @@ not False -- True
 
 
 ----------------------------------------------------
--- Lists and Tuples
+-- 2. Lists and Tuples
 ----------------------------------------------------
 
 -- Every element in a list must have the same type.
--- These two lists are the same:
+-- These two lists are equal:
 [1, 2, 3, 4, 5]
 [1..5]
 
@@ -77,11 +77,11 @@ not False -- True
 
 -- You can create a step in a range.
 [0,2..10] -- [0, 2, 4, 6, 8, 10]
-[5..1] -- This doesn't work because Haskell defaults to incrementing.
+[5..1] -- [] (Haskell defaults to incrementing)
 [5,4..1] -- [5, 4, 3, 2, 1]
 
 -- indexing into a list
-[1..10] !! 3 -- 4
+[1..10] !! 3 -- 4 (zero-based indexing)
 
 -- You can also have infinite lists in Haskell!
 [1..] -- a list of all the natural numbers
@@ -152,8 +152,8 @@ fib x
   | otherwise = fib (x - 1) + fib (x - 2)
 
 -- Pattern matching is similar. Here we have given three different
--- definitions for fib. Haskell will automatically call the first
--- function that matches the pattern of the value.
+-- equations that define fib. Haskell will automatically use the first
+-- equation whose left hand side pattern matches the value.
 fib 1 = 1
 fib 2 = 2
 fib x = fib (x - 1) + fib (x - 2)
@@ -189,20 +189,20 @@ foo = add 10 -- foo is now a function that takes a number and adds 10 to it
 foo 5 -- 15
 
 -- Another way to write the same thing
-foo = (+10)
+foo = (10+)
 foo 5 -- 15
 
 -- function composition
 -- the operator `.` chains functions together.
 -- For example, here foo is a function that takes a value. It adds 10 to it,
 -- multiplies the result of that by 4, and then returns the final value.
-foo = (*4) . (+10)
+foo = (4*) . (10+)
 
--- (5 + 10) * 4 = 60
+-- 4*(10+5) = 60
 foo 5 -- 60
 
 -- fixing precedence
--- Haskell has another operator called `$`. This operator applies a function 
+-- Haskell has an operator called `$`. This operator applies a function 
 -- to a given parameter. In contrast to standard function application, which 
 -- has highest possible priority of 10 and is left-associative, the `$` operator 
 -- has priority of 0 and is right-associative. Such a low priority means that
@@ -222,7 +222,7 @@ even . fib $ 7 -- false
 -- 5. Type signatures
 ----------------------------------------------------
 
--- Haskell has a very strong type system, and everything has a type signature.
+-- Haskell has a very strong type system, and every valid expression has a type. 
 
 -- Some basic types:
 5 :: Integer
@@ -244,10 +244,10 @@ double x = x * 2
 -- 6. Control Flow and If Expressions
 ----------------------------------------------------
 
--- if expressions
+-- if-expressions
 haskell = if 1 == 1 then "awesome" else "awful" -- haskell = "awesome"
 
--- if expressions can be on multiple lines too, indentation is important
+-- if-expressions can be on multiple lines too, indentation is important
 haskell = if 1 == 1
             then "awesome"
             else "awful"
@@ -259,7 +259,7 @@ case args of
   _ -> putStrLn "bad args"
 
 -- Haskell doesn't have loops; it uses recursion instead.
--- map applies a function over every element in an array
+-- map applies a function over every element in a list
 
 map (*2) [1..5] -- [2, 4, 6, 8, 10]
 
@@ -279,7 +279,7 @@ foldl (\x y -> 2*x + y) 4 [1,2,3] -- 43
 -- This is the same as
 (2 * (2 * (2 * 4 + 1) + 2) + 3)
 
--- foldl is left-handed, foldr is right-
+-- foldl is left-handed, foldr is right-handed
 foldr (\x y -> 2*x + y) 4 [1,2,3] -- 16
 
 -- This is now the same as
@@ -295,11 +295,10 @@ data Color = Red | Blue | Green
 
 -- Now you can use it in a function:
 
-
 say :: Color -> String
-say Red = "You are Red!"
-say Blue = "You are Blue!"
-say Green =  "You are Green!"
+say Red   = "You are Red!"
+say Blue  = "You are Blue!"
+say Green = "You are Green!"
 
 -- Your data types can have parameters too:
 
@@ -318,7 +317,7 @@ Nothing         -- of type `Maybe a` for any `a`
 -- it is not hard to explain enough to get going.
 
 -- When a Haskell program is executed, `main` is
--- called. It must return a value of type `IO ()`. For example:
+-- called. It must return a value of type `IO a` for some type `a`. For example:
 
 main :: IO ()
 main = putStrLn $ "Hello, sky! " ++ (say Blue)
@@ -361,7 +360,7 @@ sayHello = do
 -- You can think of a value of type `IO a` as representing a
 -- computer program that will generate a value of type `a`
 -- when executed (in addition to anything else it does). We can
--- store and reuse this value using `<-`. We can also
+-- name and reuse this value using `<-`. We can also
 -- make our own action of type `IO String`:
 
 action :: IO String
@@ -384,8 +383,8 @@ main'' = do
 -- The type `IO` is an example of a "monad". The way Haskell uses a monad to
 -- do IO allows it to be a purely functional language. Any function that
 -- interacts with the outside world (i.e. does IO) gets marked as `IO` in its
--- type signature. This lets us reason about what functions are "pure" (don't
--- interact with the outside world or modify state) and what functions aren't.
+-- type signature. This lets us reason about which functions are "pure" (don't
+-- interact with the outside world or modify state) and which functions aren't.
 
 -- This is a powerful feature, because it's easy to run pure functions
 -- concurrently; so, concurrency in Haskell is very easy.
@@ -432,7 +431,7 @@ Hello, Friend!
 
 There's a lot more to Haskell, including typeclasses and monads. These are the
 big ideas that make Haskell such fun to code in. I'll leave you with one final
-Haskell example: an implementation of quicksort in Haskell:
+Haskell example: an implementation of a quicksort variant in Haskell:
 
 ```haskell
 qsort [] = []