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1.17. Reformatting Paragraphs
1.17.1. Problem
Your string is too big to fit
the screen, and you want to break it up into lines of words, without
splitting a word between lines. For instance, a style correction
script might read a text file a paragraph at a time, replacing bad
phrases with good ones. Replacing a phrase like utilizes
the inherent functionality of with
uses will change the length of lines, so it must
somehow reformat the paragraphs when they're output.
1.17.2. Solution
Use the standard Text::Wrap module to put line breaks at the right
place:use Text::Wrap;
@output = wrap($leadtab, $nexttab, @para);
Or use the more discerning CPAN module, Text::Autoformat, instead:use Text::Autoformat;
$formatted = autoformat $rawtext;
1.17.3. Discussion
The Text::Wrap module provides the wrap function,
shown in Example 1-3, which takes a list of lines
and reformats them into a paragraph with no line more than
$Text::Wrap::columns characters long. We set
$columns to 20, ensuring that no line will be
longer than 20 characters. We pass wrap two
arguments before the list of lines: the first is the indent for the
first line of output, the second the indent for every subsequent
line.
Example 1-3. wrapdemo
#!/usr/bin/perl -w
# wrapdemo - show how Text::Wrap works
@input = ("Folding and splicing is the work of an editor,",
"not a mere collection of silicon",
"and",
"mobile electrons!");
use Text::Wrap qw($columns &wrap);
$columns = 20;
print "0123456789" x 2, "\n";
print wrap(" ", " ", @input), "\n";
The result of this program is:01234567890123456789
Folding and
splicing is the
work of an
editor, not a
mere collection
of silicon and
mobile electrons!
We get back a single string, with newlines ending each line but the
last:# merge multiple lines into one, then wrap one long line
use Text::Wrap;
undef $/;
print wrap('', '', split(/\s*\n\s*/, <>));
If
you have the Term::ReadKey module (available from CPAN) on your
system, you can determine your window size so you can wrap lines to
fit the current screen size. If you don't have the module, sometimes
the screen size can be found in $ENV{COLUMNS} or
by parsing the output of the stty(1) command.The following
program tries to reformat both short and long lines within a
paragraph, similar to the fmt(1) program, by
setting the input record separator $/ to the empty
string (causing <> to read paragraphs) and
the output record separator $\ to two newlines.
Then the paragraph is converted into one long line by changing all
newlines and any surrounding whitespace to single spaces. Finally, we
call the wrap function with leading and subsequent
tab strings set to the empty string so we can have block paragraphs.use Text::Wrap qw(&wrap $columns);
use Term::ReadKey qw(GetTerminalSize);
($columns) = GetTerminalSize( );
($/, $\) = ('', "\n\n"); # read by paragraph, output 2 newlines
while (<>) { # grab a full paragraph
s/\s*\n\s*/ /g; # convert intervening newlines to spaces
print wrap('', '', $_); # and format
}
The CPAN module Text::Autoformat is much more clever. For one thing,
it tries to avoid "widows," that is, very short lines at the end.
More remarkably, it correctly copes with reformatting paragraphs that
have multiple, deeply nested citations. An example from that module's
manpage shows how the module can painlessly convert:In comp.lang.perl.misc you wrote:
: > <CN = Clooless Noobie> writes:
: > CN> PERL sux because:
: > CN> * It doesn't have a switch statement and you have to put $
: > CN>signs in front of everything
: > CN> * There are too many OR operators: having |, || and 'or'
: > CN>operators is confusing
: > CN> * VB rools, yeah!!!!!!!!!
: > CN> So anyway, how can I stop reloads on a web page?
: > CN> Email replies only, thanks - I don't read this newsgroup.
: >
: > Begone, sirrah! You are a pathetic, Bill-loving, microcephalic
: > script-infant.
: Sheesh, what's with this group - ask a question, get toasted! And how
: *dare* you accuse me of Ianuphilia!
into:In comp.lang.perl.misc you wrote:
: > <CN = Clooless Noobie> writes:
: > CN> PERL sux because:
: > CN> * It doesn't have a switch statement and you
: > CN> have to put $ signs in front of everything
: > CN> * There are too many OR operators: having |, ||
: > CN> and 'or' operators is confusing
: > CN> * VB rools, yeah!!!!!!!!! So anyway, how can I
: > CN> stop reloads on a web page? Email replies
: > CN> only, thanks - I don't read this newsgroup.
: >
: > Begone, sirrah! You are a pathetic, Bill-loving,
: > microcephalic script-infant.
: Sheesh, what's with this group - ask a question, get toasted!
: And how *dare* you accuse me of Ianuphilia!
simply via print autoformat($badparagraph). Pretty
impressive, eh?Here's a miniprogram that uses that module to reformat each paragraph
of its input stream:use Text::Autoformat;
$/ = '';
while (<>) {
print autoformat($_, {squeeze => 0, all => 1}), "\n";
}
1.17.4. See Also
The split and join functions in
perlfunc(1) and Chapter 29 of
Programming Perl; the manpage for the standard
Text::Wrap module; the CPAN module Term::ReadKey, and its use in
Recipe 15.6 and the CPAN module
Text::Autoformat
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