Patch #731514: Update recursion documentation to mention simple recursion.

1 files changed, 14 insertions, 11 deletions

diff --git a/Doc/lib/libre.tex b/Doc/lib/libre.tex
index c2c7a6f..cf05441 100644
--- a/Doc/lib/libre.tex
+++ b/Doc/lib/libre.tex
@@ -896,15 +896,16 @@ The equivalent regular expression would be
     (\S+) - (\d+) errors, (\d+) warnings
 \end{verbatim}
 
-\leftline{\strong{Avoiding backtracking}}
+\leftline{\strong{Avoiding recursion}}
 
-If you create regular expressions that require the engine to perform a lot
-of backtracking, you may encounter a RuntimeError exception with the message
-\code{maximum recursion limit exceeded}.  For example,
+If you create regular expressions that require the engine to perform a
+lot of recursion, you may encounter a RuntimeError exception with
+the message \code{maximum recursion limit} exceeded. For example,
 
 \begin{verbatim}
->>> s = "<" + "that's a very big string!"*1000 + ">"
->>> re.match('<.*?>', s)
+>>> import re
+>>> s = 'Begin ' + 1000*'a very long string ' + 'end'
+>>> re.match('Begin (\w| )*? end', s).end()
 Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "/usr/local/lib/python2.3/sre.py", line 132, in match
@@ -912,8 +913,10 @@ Traceback (most recent call last):
 RuntimeError: maximum recursion limit exceeded
 \end{verbatim}
 
-You can often restructure your regular expression to avoid backtracking.
-The above regular expression can be recast as
-\regexp{\textless[\textasciicircum \textgreater]*\textgreater}.  As a
-further benefit, such regular expressions will run faster than their
-backtracking equivalents.
+You can often restructure your regular expression to avoid recursion.
+
+\versionadded[Simple uses of the \regexp{*?} pattern are now
+special-cased to avoid recursion.  Thus, the above regular expression
+can avoid recursion by being recast as \regexp{Begin [a-zA-Z0-9_ ]*?end}.
+As a further benefit, such regular expressions will run faster than
+their recursive equivalents.]{2.3}