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SF bug #803842: Wrong description of regexp concatenation

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Raymond Hettinger 2003-09-10 18:45:12 +00:00
parent 4997a69fe4
commit 5bcc933211
1 changed files with 5 additions and 4 deletions
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@ -51,10 +51,11 @@ matches a particular string, which comes down to the same thing).
Regular expressions can be concatenated to form new regular
expressions; if \emph{A} and \emph{B} are both regular expressions,
then \emph{AB} is also a regular expression. If a string \emph{p}
matches A and another string \emph{q} matches B, the string \emph{pq}
will match AB if \emph{A} and \emph{B} do no specify boundary
conditions that are no longer satisfied by \emph{pq}. Thus, complex
then \emph{AB} is also a regular expression. In general, if a string
\emph{p} matches \emph{A} and another string \emph{q} matches \emph{B},
the string \emph{pq} will match AB. This holds unless \emph{A} or
\emph{B} contain low precedence operations; boundary conditions between
\emph{A} and \emph{B}; or have numbered group references. Thus, complex
expressions can easily be constructed from simpler primitive
expressions like the ones described here. For details of the theory
and implementation of regular expressions, consult the Friedl book