Make sure "del d[n]" is properly supported. Was necessary because the
same method that implements __setitem__ also implements __delitem__.
Also, there were several good use cases (removing items from a queue
and implementing Forth style stack ops).
diff --git a/Doc/lib/libcollections.tex b/Doc/lib/libcollections.tex
index 148ddea..c7d5c50 100644
--- a/Doc/lib/libcollections.tex
+++ b/Doc/lib/libcollections.tex
@@ -137,24 +137,21 @@
The \method{rotate()} method provides a way to implement \class{deque}
slicing and deletion:
+This pure python implementation of \code{del d[n]} shows how to use the
+\method{rotate()} method as a building block for implementing a variety
+of class{deque} operations:
+
\begin{verbatim}
def delete_nth(d, n):
- "del d[n]"
d.rotate(-n)
d.popleft()
d.rotate(n)
-
->>> d = deque('abcdef')
->>> delete_nth(d, 2) # remove the entry at d[2]
->>> d
-deque(['a', 'b', 'd', 'e', 'f'])
-
\end{verbatim}
-For slicing, the idea is the same. Use \method{rotate()} to bring a target
-element to the left side of the deque. Remove old entries with
-\method{popleft()}, add new entries with \method{extend()}, and then
-reverse the rotation.
+To implement \class{deque} slicing, use a similar approach applying
+\method{rotate()} to bring a target element to the left side of the deque.
+Remove old entries with \method{popleft()}, add new entries with
+\method{extend()}, and then reverse the rotation.
With minor variations on that approach, it is easy to implement Forth style
stack manipulations such as \code{dup}, \code{drop}, \code{swap}, \code{over},