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(Regexp Replace): Rewrite description of \# \, and \?.

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Richard M. Stallman 2004-06-25 21:28:14 +00:00
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@ -1,3 +1,7 @@
2004-06-25 Richard M. Stallman <rms@gnu.org>
* search.texi (Regexp Replace): Rewrite description of \# \, and \?.
2004-06-25 David Kastrup <dak@gnu.org>
* search.texi (Regexp Replace): Some typo corrections and

67
man/search.texi
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@ -993,13 +993,15 @@ in your text.
single string. The similar command @kbd{M-x replace-regexp} replaces
any match for a specified pattern.
In @code{replace-regexp}, the @var{newstring} need not be constant: it
can refer to all or part of what is matched by the @var{regexp}.
@samp{\&} in @var{newstring} stands for the entire match being replaced.
@samp{\@var{d}} in @var{newstring}, where @var{d} is a digit, stands for
whatever matched the @var{d}th parenthesized grouping in @var{regexp}.
To include a @samp{\} in the text to replace with, you must enter
@samp{\\}. For example,
In @code{replace-regexp}, the @var{newstring} need not be constant:
it can refer to all or part of what is matched by the @var{regexp}.
@samp{\&} in @var{newstring} stands for the entire match being
replaced. @samp{\@var{d}} in @var{newstring}, where @var{d} is a
digit, stands for whatever matched the @var{d}th parenthesized
grouping in @var{regexp}. @samp{\#} refers to the count of
replacements already made in this command, as a decimal number. In
the first replacement, @samp{\#} stands for @samp{0}; in the second,
for @samp{1}; and so on. For example,
@example
M-x replace-regexp @key{RET} c[ad]+r @key{RET} \&-safe @key{RET}
@ -1014,17 +1016,26 @@ M-x replace-regexp @key{RET} \(c[ad]+r\)-safe @key{RET} \1 @key{RET}
@end example
@noindent
performs the inverse transformation.
performs the inverse transformation. To include a @samp{\} in the
text to replace with, you must enter @samp{\\}.
You can also use arbitrary Lisp expressions evaluated at replacement
time by placing @samp{\,} before them in the replacement string. Inside
of those expressions, the symbols @samp{\&} and @samp{\@var{n}} refer to
match and submatch strings like described above (though @var{n} may
exceed 9 here, and you get @code{nil} if nothing matches). @samp{\#&}
and @samp{\#@var{n}} refer to those strings converted to numbers.
@samp{\#} is short for @samp{replace-count}, the number of already
completed replacements. This particular shorthand can also be used
outside of @samp{\,}.
You can also use Lisp expressions to calculate parts of the
replacement string. To do this, write @samp{\,} followed by the
expression in the replacement string. Each replacement calculates the
value of the expression, which ought to be a string, and uses it in
the replacement string in place of the expression itself. If the
expression is a symbol, one space in the replacement string after the
symbol name counts as part of the symbol name, so the value replaces
them both.
Inside such an expression, @samp{\&} and @samp{\@var{n}} used as
subexpressions refer respectively to the entire match as a string, and
to a submatch as a string. @var{n} may exceed 9 here, and the value
of @samp{\@var{n}} is @code{nil} if subexpression @var{n} did not
match. You can also use @samp{\#&} and @samp{\#@var{n}} refer to
those matches converted to numbers (this is valid when the match or
submatch has the form of a number). @samp{\#} stands for the number
of already-completed replacements.
Repeating our example to exchange @samp{x} and @samp{y}, we can thus
do it also this way:
@ -1034,21 +1045,21 @@ M-x replace-regexp @key{RET} \(x\)\|y @key{RET}
\,(if \1 "y" "x") @key{RET}
@end example
One function that comes handy in Lisp replacements is @samp{format}
(@pxref{Formatting Strings,,,elisp, GNU Emacs Lisp Reference Manual}).
For example, to add consecutively numbered strings like @samp{ABC00042}
to columns 73 @w{to 80} (unless they are already occupied), you can use
The @code{format} function (@pxref{Formatting Strings,,,elisp, GNU
Emacs Lisp Reference Manual}) comes in handy for computing replacement
strings for @samp{\,}. For example, to add consecutively numbered
strings like @samp{ABC00042} to columns 73 @w{to 80} (unless they are
already occupied), you can use
@example
M-x replace-regexp @key{RET} ^.\@{0,72\@}$ @key{RET}
\,(format "%-72sABC%05d" \& \#) @key{RET}
@end example
Another feature you can use in the replacement string of Regexp
commands is @samp{\?}. In that case you will be allowed to edit the
replacement string at the given position before the replacement gets
performed. Lisp style replacements are performed before @samp{\?} gets
executed. For example,
If you want to enter part of the replacement string by hand each
time, use @samp{\?} in the replacement string. Each replacement will
enter a recursive edit, with point at the position where the @samp{\?}
was. For example,
@example
M-x replace-regexp @key{RET} \footnote@{ @key{RET}
@ -1058,8 +1069,8 @@ M-x replace-regexp @key{RET} \footnote@{ @key{RET}
@noindent
will add labels starting with @samp{\label@{fn:0@}} to occurences of
@samp{\footnote@{}, but letting you edit each replacement before
performing it. If you want labels starting at 1, use @samp{\,(1+ \#)}
instead of @samp{\#}.
performing it. To number the labels starting at 1, use @samp{\,(1+
\#)} instead of @samp{\#}.
@node Replacement and Case, Query Replace, Regexp Replace, Replace
@subsection Replace Commands and Case