Correct typos and add bits of discussion. Also add another "chief

virtue".

pep-0234.txt

@@ -19,7 +19,7 @@ Abstract
 
     In addition, specific iterators over the keys of a dictionary and
     over the lines of a file are proposed, and a proposal is made to
-    allow spelling dict.kas_key(key) as "key in dict".
+    allow spelling dict.has_key(key) as "key in dict".
 
     Note: this is an almost complete rewrite of this PEP by the second
     author, describing the actual implementation checked into the
@@ -116,14 +116,14 @@ Python API Specification
       return value does not equal the sentinel, it is returned as the
       next value from the iterator.  If the callable raises an
       exception, this is propagated normally; in particular, the
-      function is allowed to raise StopError as an alternative way to
+      function is allowed to raise StopIteration as an alternative way
-      end the iteration.  (This functionality is available from the C
+      to end the iteration.  (This functionality is available from the
-      API as PyCallIter_New(callable, sentinel).)
+      C API as PyCallIter_New(callable, sentinel).)
 
     Iterator objects returned by either form of iter() have a next()
     method.  This method either returns the next value in the
-    iteration, or raises StopError (or a derived exception class) to
+    iteration, or raises StopIteration (or a derived exception class)
-    signal the end of the iteration.  Any other exception should be
+    to signal the end of the iteration.  Any other exception should be
     considered to signify an error and should be propagated normally,
     not taken to mean the end of the iteration.
 
@@ -212,11 +212,11 @@ Rationale
 
     If all the parts of the proposal are included, this addresses many
     concerns in a consistent and flexible fashion.  Among its chief
-    virtues are the following three -- no, four -- no, five -- points:
+    virtues are the following four -- no, five -- no, six -- points:
 
     1. It provides an extensible iterator interface.
 
-    1. It allows performance enhancements to list iteration.
+    2. It allows performance enhancements to list iteration.
 
     3. It allows big performance enhancements to dictionary iteration.
 
@@ -228,18 +228,24 @@ Rationale
        mappings, even mappings that only implement a subset of
        {__getitem__, keys, values, items}.
 
+    6. It makes code iterating over non-sequence collections more
+       concise and readable.
+
 
 Open Issues
 
     The following questions are still open.
 
     - The name iter() is an abbreviation.  Alternatives proposed
-      include iterate(), harp(), traverse(), narrate().
+      include iterate(), traverse(), but these appear too long.
+      Python has a history of using abbrs for common builtins,
+      e.g. repr(), str(), len().
 
     - Using the same name for two different operations (getting an
       iterator from an object and making an iterator for a function
       with an sentinel value) is somewhat ugly.  I haven't seen a
-      better name for the second operation though.
+      better name for the second operation though, and since they both
+      return an iterator, it's easy to remember.
 
     - Once a particular iterator object has raised StopIteration, will
       it also raise StopIteration on all subsequent next() calls?
@@ -286,8 +292,18 @@ Open Issues
       this is true, I (Guido) find the correspondence between "for x in
       dict" and "if x in dict" too compelling to break, and there's not
       much overhead in having to write dict[x] to explicitly get the
-      value.  We could also add methods to dictionaries that return
+      value.  I've also timed the difference between
-      different kinds of iterators, e.g.
+
+          for key in dict: dict[key]
+
+      and
+
+          for key, value in dict[key]: pass
+
+      and found that these run at about the same speed.
+
+      We could also add methods to dictionaries that return different
+      kinds of iterators, e.g.
 
           for key, value in dict.iteritems(): ...