Merge pull request #63 from tesujimath/guide-operator-precedence

Fix the operator precedence examples.

Author: thomashoneyman

GUIDE.md

@@ -94,20 +94,24 @@ post =
 
 postEdit :: Match MyRoute
 postEdit =
-  PostEdit <$> (lit "posts" *> int <* lit "edit")
+  PostEdit <$> (lit "posts" *> int) <* lit "edit"
 ```
 
 Note the use of the `*>` and `<*` operators. These let us direct the focus of
 the value we want to consume. In `postEdit`, we want to consume the `int`,
 but we also need to match the "edit" suffix. The arrows point to the value we
 want.
 
+Note that in general parentheses are required when using `*>` since the
+operator precedence is not what is required (resulting in type errors
+otherwise.)
+
 And now finally, we need to extract multiple segments for `PostBrowse`.
 
 ```purescript
 postBrowse :: Match MyRoute
 postBrowse =
-  PostBrowse <$> (lit "posts" *> str <*> str)
+  PostBrowse <$> (lit "posts" *> str) <*> str
 ```
 
 The `<*>` combinator has arrows on both sides because we want both values.
@@ -145,8 +149,8 @@ myRoute :: Match MyRoute
 myRoute = oneOf
   [ PostIndex <$ lit "posts"
   , Post <$> (lit "posts" *> int)
-  , PostEdit <$> (lit "posts" *> int <* lit "edit")
-  , PostBrowse <$> (lit "posts" *> str <*> str)
+  , PostEdit <$> (lit "posts" *> int) <* lit "edit"
+  , PostBrowse <$> (lit "posts" *> str) <*> str
   ]
 ```
 
@@ -161,8 +165,8 @@ myRoute =
   lit "posts" *> oneOf
     [ pure PostIndex
     , Post <$> int
-    , PostEdit <$> (int <* lit "edit")
-    , PostBrowse <$> (str <*> str)
+    , PostEdit <$> int <* lit "edit"
+    , PostBrowse <$> str <*> str
     ]
 ```
 
@@ -179,9 +183,9 @@ myRoute :: Match MyRoute
 myRoute =
   lit "posts" *> oneOf
     [ PostIndex <$ end
-    , Post <$> (int <* end)
-    , PostEdit <$> (int <* lit "edit" <* end)
-    , PostBrowse <$> (str <*> str <* end)
+    , Post <$> int <* end
+    , PostEdit <$> int <* lit "edit" <* end
+    , PostBrowse <$> str <*> str <* end
     ]
 ```
 
@@ -193,9 +197,9 @@ the routes followed by an `end`, so we would still have to rearrange them.
 myRoute :: Match MyRoute
 myRoute =
   lit "posts" *> oneOf
-    [ PostEdit <$> (int <* lit "edit")
+    [ PostEdit <$> int <* lit "edit"
     , Post <$> int
-    , PostBrowse <$> (str <*> str)
+    , PostBrowse <$> str <*> str
     , pure PostIndex
     ] <* end
 ```
@@ -211,9 +215,9 @@ with the `root` combinator.
 myRoute :: Match MyRoute
 myRoute =
   root *> lit "posts" *> oneOf
-    [ PostEdit <$> (int <* lit "edit")
+    [ PostEdit <$> int <* lit "edit"
     , Post <$> int
-    , PostBrowse <$> (str <*> str)
+    , PostBrowse <$> str <*> str
     , pure PostIndex
     ] <* end
 ```