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Guido van Rossum 1996-10-24 22:49:13 +00:00
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28
Doc/lib/libregex.tex
View file

@ -4,8 +4,8 @@
This module provides regular expression matching operations similar to This module provides regular expression matching operations similar to
those found in Emacs. It is always available. those found in Emacs. It is always available.
By default the patterns are Emacs-style regular expressions, By default the patterns are Emacs-style regular expressions
with one exception. There is (with one exception). There is
a way to change the syntax to match that of several well-known a way to change the syntax to match that of several well-known
\UNIX{} utilities. The exception is that Emacs' \samp{\e s} \UNIX{} utilities. The exception is that Emacs' \samp{\e s}
pattern is not supported, since the original implementation references pattern is not supported, since the original implementation references
@ -36,7 +36,8 @@ avoid interpretation as an octal escape.
A regular expression (or RE) specifies a set of strings that matches A regular expression (or RE) specifies a set of strings that matches
it; the functions in this module let you check if a particular string it; the functions in this module let you check if a particular string
matches a given regular expression. matches a given regular expression (or if a given regular expression
matches a particular string, which comes down to the same thing).
Regular expressions can be concatenated to form new regular Regular expressions can be concatenated to form new regular
expressions; if \emph{A} and \emph{B} are both regular expressions, expressions; if \emph{A} and \emph{B} are both regular expressions,
@ -51,22 +52,23 @@ any textbook about compiler construction.
% "Compilers: Principles, Techniques and Tools", by Alfred V. Aho, % "Compilers: Principles, Techniques and Tools", by Alfred V. Aho,
% Ravi Sethi, and Jeffrey D. Ullman, or some FA text. % Ravi Sethi, and Jeffrey D. Ullman, or some FA text.
A brief explanation of the format of regular A brief explanation of the format of regular expressions follows.
expressions follows.
Regular expressions can contain both special and ordinary characters. Regular expressions can contain both special and ordinary characters.
Ordinary characters, like '\code{A}', '\code{a}', or '\code{0}', are Ordinary characters, like '\code{A}', '\code{a}', or '\code{0}', are
the simplest regular expressions; they simply match themselves. You the simplest regular expressions; they simply match themselves. You
can concatenate ordinary characters, so '\code{last}' matches the can concatenate ordinary characters, so '\code{last}' matches the
characters 'last'. characters 'last'. (In the rest of this section, we'll write RE's in
\code{this special font}, usually without quotes, and strings to be
matched 'in single quotes'.)
Special characters either stand for classes of ordinary characters, or Special characters either stand for classes of ordinary characters, or
affect how the regular expressions around them are interpreted. affect how the regular expressions around them are interpreted.
The special characters are: The special characters are:
\begin{itemize} \begin{itemize}
\item[\code{.}]{Matches any character except a newline.} \item[\code{.}]{(Dot.) Matches any character except a newline.}
\item[\code{\^}]{Matches the start of the string.} \item[\code{\^}]{(Caret.) Matches the start of the string.}
\item[\code{\$}]{Matches the end of the string. \item[\code{\$}]{Matches the end of the string.
\code{foo} matches both 'foo' and 'foobar', while the regular \code{foo} matches both 'foo' and 'foobar', while the regular
expression '\code{foo\$}' matches only 'foo'.} expression '\code{foo\$}' matches only 'foo'.}
@ -114,7 +116,8 @@ should be doubled are indicated.
\begin{itemize} \begin{itemize}
\item[\code{\e|}]\code{A\e|B}, where A and B can be arbitrary REs, \item[\code{\e|}]\code{A\e|B}, where A and B can be arbitrary REs,
creates a regular expression that will match either A or B. creates a regular expression that will match either A or B. This can
be used inside groups (see below) as well.
% %
\item[\code{\e( \e)}]{Indicates the start and end of a group; the \item[\code{\e( \e)}]{Indicates the start and end of a group; the
contents of a group can be matched later in the string with the contents of a group can be matched later in the string with the
@ -126,7 +129,8 @@ number. For example, \code{\e (.+\e ) \e \e 1} matches 'the the' or
'55 55', but not 'the end' (note the space after the group). This '55 55', but not 'the end' (note the space after the group). This
special sequence can only be used to match one of the first 9 groups; special sequence can only be used to match one of the first 9 groups;
groups with higher numbers can be matched using the \code{\e v} groups with higher numbers can be matched using the \code{\e v}
sequence.}} sequence. (\code{\e 8} and \code{\e 9} don't need a double backslash
because they are not octal digits.)}}
% %
\item[\code{\e \e b}]{Matches the empty string, but only at the \item[\code{\e \e b}]{Matches the empty string, but only at the
beginning or end of a word. A word is defined as a sequence of beginning or end of a word. A word is defined as a sequence of
@ -151,6 +155,8 @@ character.}
\item[\code{\e >}]{Matches the empty string, but only at the end of a \item[\code{\e >}]{Matches the empty string, but only at the end of a
word.} word.}
\item[\code{\e \e \e \e}]{Matches a literal backslash.}
% In Emacs, the following two are start of buffer/end of buffer. In % In Emacs, the following two are start of buffer/end of buffer. In
% Python they seem to be synonyms for ^$. % Python they seem to be synonyms for ^$.
\item[\code{\e `}]{Like \code{\^}, this only matches at the start of the \item[\code{\e `}]{Like \code{\^}, this only matches at the start of the
@ -175,7 +181,7 @@ The module defines these functions, and an exception:
\begin{funcdesc}{search}{pattern\, string} \begin{funcdesc}{search}{pattern\, string}
Return the first position in \var{string} that matches the regular Return the first position in \var{string} that matches the regular
expression \var{pattern}. Return -1 if no position in the string expression \var{pattern}. Return \code{-1} if no position in the string
matches the pattern (this is different from a zero-length match matches the pattern (this is different from a zero-length match
anywhere!). anywhere!).
\end{funcdesc} \end{funcdesc}

28
Doc/libregex.tex
View file

@ -4,8 +4,8 @@
This module provides regular expression matching operations similar to This module provides regular expression matching operations similar to
those found in Emacs. It is always available. those found in Emacs. It is always available.
By default the patterns are Emacs-style regular expressions, By default the patterns are Emacs-style regular expressions
with one exception. There is (with one exception). There is
a way to change the syntax to match that of several well-known a way to change the syntax to match that of several well-known
\UNIX{} utilities. The exception is that Emacs' \samp{\e s} \UNIX{} utilities. The exception is that Emacs' \samp{\e s}
pattern is not supported, since the original implementation references pattern is not supported, since the original implementation references
@ -36,7 +36,8 @@ avoid interpretation as an octal escape.
A regular expression (or RE) specifies a set of strings that matches A regular expression (or RE) specifies a set of strings that matches
it; the functions in this module let you check if a particular string it; the functions in this module let you check if a particular string
matches a given regular expression. matches a given regular expression (or if a given regular expression
matches a particular string, which comes down to the same thing).
Regular expressions can be concatenated to form new regular Regular expressions can be concatenated to form new regular
expressions; if \emph{A} and \emph{B} are both regular expressions, expressions; if \emph{A} and \emph{B} are both regular expressions,
@ -51,22 +52,23 @@ any textbook about compiler construction.
% "Compilers: Principles, Techniques and Tools", by Alfred V. Aho, % "Compilers: Principles, Techniques and Tools", by Alfred V. Aho,
% Ravi Sethi, and Jeffrey D. Ullman, or some FA text. % Ravi Sethi, and Jeffrey D. Ullman, or some FA text.
A brief explanation of the format of regular A brief explanation of the format of regular expressions follows.
expressions follows.
Regular expressions can contain both special and ordinary characters. Regular expressions can contain both special and ordinary characters.
Ordinary characters, like '\code{A}', '\code{a}', or '\code{0}', are Ordinary characters, like '\code{A}', '\code{a}', or '\code{0}', are
the simplest regular expressions; they simply match themselves. You the simplest regular expressions; they simply match themselves. You
can concatenate ordinary characters, so '\code{last}' matches the can concatenate ordinary characters, so '\code{last}' matches the
characters 'last'. characters 'last'. (In the rest of this section, we'll write RE's in
\code{this special font}, usually without quotes, and strings to be
matched 'in single quotes'.)
Special characters either stand for classes of ordinary characters, or Special characters either stand for classes of ordinary characters, or
affect how the regular expressions around them are interpreted. affect how the regular expressions around them are interpreted.
The special characters are: The special characters are:
\begin{itemize} \begin{itemize}
\item[\code{.}]{Matches any character except a newline.} \item[\code{.}]{(Dot.) Matches any character except a newline.}
\item[\code{\^}]{Matches the start of the string.} \item[\code{\^}]{(Caret.) Matches the start of the string.}
\item[\code{\$}]{Matches the end of the string. \item[\code{\$}]{Matches the end of the string.
\code{foo} matches both 'foo' and 'foobar', while the regular \code{foo} matches both 'foo' and 'foobar', while the regular
expression '\code{foo\$}' matches only 'foo'.} expression '\code{foo\$}' matches only 'foo'.}
@ -114,7 +116,8 @@ should be doubled are indicated.
\begin{itemize} \begin{itemize}
\item[\code{\e|}]\code{A\e|B}, where A and B can be arbitrary REs, \item[\code{\e|}]\code{A\e|B}, where A and B can be arbitrary REs,
creates a regular expression that will match either A or B. creates a regular expression that will match either A or B. This can
be used inside groups (see below) as well.
% %
\item[\code{\e( \e)}]{Indicates the start and end of a group; the \item[\code{\e( \e)}]{Indicates the start and end of a group; the
contents of a group can be matched later in the string with the contents of a group can be matched later in the string with the
@ -126,7 +129,8 @@ number. For example, \code{\e (.+\e ) \e \e 1} matches 'the the' or
'55 55', but not 'the end' (note the space after the group). This '55 55', but not 'the end' (note the space after the group). This
special sequence can only be used to match one of the first 9 groups; special sequence can only be used to match one of the first 9 groups;
groups with higher numbers can be matched using the \code{\e v} groups with higher numbers can be matched using the \code{\e v}
sequence.}} sequence. (\code{\e 8} and \code{\e 9} don't need a double backslash
because they are not octal digits.)}}
% %
\item[\code{\e \e b}]{Matches the empty string, but only at the \item[\code{\e \e b}]{Matches the empty string, but only at the
beginning or end of a word. A word is defined as a sequence of beginning or end of a word. A word is defined as a sequence of
@ -151,6 +155,8 @@ character.}
\item[\code{\e >}]{Matches the empty string, but only at the end of a \item[\code{\e >}]{Matches the empty string, but only at the end of a
word.} word.}
\item[\code{\e \e \e \e}]{Matches a literal backslash.}
% In Emacs, the following two are start of buffer/end of buffer. In % In Emacs, the following two are start of buffer/end of buffer. In
% Python they seem to be synonyms for ^$. % Python they seem to be synonyms for ^$.
\item[\code{\e `}]{Like \code{\^}, this only matches at the start of the \item[\code{\e `}]{Like \code{\^}, this only matches at the start of the
@ -175,7 +181,7 @@ The module defines these functions, and an exception:
\begin{funcdesc}{search}{pattern\, string} \begin{funcdesc}{search}{pattern\, string}
Return the first position in \var{string} that matches the regular Return the first position in \var{string} that matches the regular
expression \var{pattern}. Return -1 if no position in the string expression \var{pattern}. Return \code{-1} if no position in the string
matches the pattern (this is different from a zero-length match matches the pattern (this is different from a zero-length match
anywhere!). anywhere!).
\end{funcdesc} \end{funcdesc}