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Text::Autoformat - Automatic text wrapping and reformatting |
Text::Autoformat - Automatic text wrapping and reformatting
This document describes version 1.12 of Text::Autoformat, released May 27, 2003.
# Minimal use: read from STDIN, format to STDOUT...
use Text::Autoformat;
autoformat;
# In-memory formatting...
$formatted = autoformat $rawtext;
# Configuration...
$formatted = autoformat $rawtext, { %options };
# Margins (1..72 by default)...
$formatted = autoformat $rawtext, { left=>8, right=>70 };
# Justification (left by default)...
$formatted = autoformat $rawtext, { justify => 'left' };
$formatted = autoformat $rawtext, { justify => 'right' };
$formatted = autoformat $rawtext, { justify => 'full' };
$formatted = autoformat $rawtext, { justify => 'centre' };
# Filling (does so by default)...
$formatted = autoformat $rawtext, { fill=>0 };
# Squeezing whitespace (does so by default)...
$formatted = autoformat $rawtext, { squeeze=>0 };
# Case conversions...
$formatted = autoformat $rawtext, { case => 'lower' };
$formatted = autoformat $rawtext, { case => 'upper' };
$formatted = autoformat $rawtext, { case => 'sentence' };
$formatted = autoformat $rawtext, { case => 'title' };
$formatted = autoformat $rawtext, { case => 'highlight' };
# Selective reformatting
$formatted = autoformat $rawtext, { ignore=>qr/^\t/ };
Perl plaintext formatters just aren't smart enough. Given a typical piece of plaintext in need of formatting:
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!
both the venerable Unix fmt tool and Perl's standard Text::Wrap module produce:
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!
Other formatting modules -- such as Text::Correct and Text::Format -- provide more control over their output, but produce equally poor results when applied to arbitrary input. They simply don't understand the structural conventions of the text they're reformatting.
The Text::Autoformat module provides a subroutine named autoformat that
wraps text to specified margins. However, autoformat reformats its
input by analysing the text's structure, so it wraps the above example
like so:
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!
Note that the various quoting conventions have been observed. In fact,
their structure has been used to determine where some paragraphs begin.
Furthermore autoformat correctly distinguished between the leading
'*' bullets of the nested list (which were outdented) and the leading
emphatic '*' of ``*dare*'' (which was inlined).
The fundamental task of the autoformat subroutine is to identify and
rearrange independent paragraphs in a text. Paragraphs typically consist
of a series of lines containing at least one non-whitespace character,
followed by one or more lines containing only optional whitespace.
This is a more liberal definition than many other formatters
use: most require an empty line to terminate a paragraph. Paragraphs may
also be denoted by bulleting, numbering, or quoting (see the following
sections).
Once a paragraph has been isolated, autoformat fills and re-wraps its
lines according to the margins that are specified in its argument list.
These are placed after the text to be formatted, in a hash reference:
$tidied = autoformat($messy, {left=>20, right=>60});
By default, autoformat uses a left margin of 1 (first column) and a
right margin of 72.
You can also control whether (and how) autoformat breaks words at the
end of a line, using the 'break' option:
# Turn off all hyphenation
use Text::Autoformat qw(autoformat break_wrap);
$tidied = autoformat($messy, {break=>break_wrap});
# Default hyphenation
use Text::Autoformat qw(autoformat break_at);
$tidied = autoformat($messy, {break=>break_at('-')});
# Use TeX::Hyphen module's hyphenation (module must be installed)
use Text::Autoformat qw(autoformat break_TeX);
$tidied = autoformat($messy, {break=>break_TeX});
Normally, autoformat only reformats the first paragraph it encounters,
and leaves the remainder of the text unaltered. This behaviour is useful
because it allows a one-liner invoking the subroutine to be mapped
onto a convenient keystroke in a text editor, to provide
one-paragraph-at-a-time reformatting:
% cat .exrc
map f !Gperl -MText::Autoformat -e'autoformat'
(Note that to facilitate such one-liners, if autoformat is called
in a void context without any text data, it takes its text from
STDIN and writes its result to STDOUT).
To enable autoformat to rearrange the entire input text at once, the
all argument is used:
$tidied_all = autoformat($messy, {left=>20, right=>60, all=>1});
autoformat can also be directed to selectively reformat paragraphs,
using the ignore argument:
$tidied_some = autoformat($messy, {ignore=>qr/^[ \t]/});
The value for ignore may be a qr'd regex, a subroutine reference,
or the special string 'indented'.
If a regex is specified, any paragraph whose original text matches that regex will not be reformatted (i.e. it will be printed verbatim).
If a subroutine is specified, that subroutine will be called once for
each paragraph (with $_ set to the paragraph's text). The subroutine is
expected to return a true or false value. If it returns true, the
paragraph will not be reformatted.
If the value of the ignore option is the string 'indented',
autoformat will ignore any paragraph in which every line begins with a
whitespace.
Often plaintext will include lists that are either:
* bulleted,
* simply numbered (i.e. 1., 2., 3., etc.), or
* hierarchically numbered (1, 1.1, 1.2, 1.3, 2, 2.1. and so forth).
In such lists, each bulleted item is implicitly a separate paragraph, and is formatted individually, with the appropriate indentation:
* bulleted,
* simply numbered (i.e. 1., 2., 3.,
etc.), or
* hierarchically numbered (1, 1.1,
1.2, 1.3, 2, 2.1. and so forth).
More importantly, if the points are numbered, the numbering is checked and reordered. For example, a list whose points have been rearranged:
2. Analyze problem
3. Design algorithm
1. Code solution
5. Test
4. Ship
would be renumbered automatically by autoformat:
1. Analyze problem
2. Design algorithm
3. Code solution
4. Ship
5. Test
The same reordering would be performed if the ``numbering'' was by letters
(a. b. c. etc.) or Roman numerals (i. ii. iii.) or by
some combination of these (1a. 1b. 2a. 2b. etc.) Handling
disordered lists of letters and Roman numerals presents an interesting
challenge. A list such as:
C. Put cat in box.
D. Close lid.
E. Activate Geiger counter.
should be reordered as A. B. C., whereas:
C. Put cat in box.
D. Close lid.
XLI. Activate Geiger counter.
should be reordered I. II. III.
The autoformat subroutine solves this problem by always interpreting
alphabetic bullets as being letters, unless the full list consists
only of valid Roman numerals, at least one of which is two or
more characters long.
If automatic renumbering isn't wanted, just specify the 'renumber'
option with a false value.
Note that numbers above 1000 at the start of a line are no longer considered to be paragraph numbering. Numbered paragraphs running that high are exceptionally rare, and much rarer than paragraphs that look like this:
Although it has long been popular (especially in the year
2001) to point out that we now live in the Future, many
of the promised miracles of Future Life have failed to
eventuate. This is a new phenomenon (it didn't happen in
1001) because the idea that the future might be different
is a new phenomenon.
which the former numbering rules caused to be formatted like this:
Although it has long been popular (especially in the year
2001) to point out that we now live in the Future, many of the
promised miracles of Future Life have failed to eventuate.
This is a new phenomenon (it didn't happen in
2002) because the idea that the future might be different is a
new phenomenon.
but which are now formatted:
Although it has long been popular (especially in the year 2001)
to point out that we now live in the Future, many of the
promised miracles of Future Life have failed to eventuate. This
is a new phenomenon (it didn't happen in 1001) because the idea
that the future might be different is a new phenomenon.
Another case in which contiguous lines may be interpreted as belonging to different paragraphs, is where they are quoted with distinct quoters. For example:
: > CN> So anyway, how can I stop reloads on a web page? Email
: > CN> 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!
autoformat recognizes the various quoting conventions used in this
example and treats it as three paragraphs to be independently
reformatted.
Block quotations present a different challenge. A typical formatter would render the following quotation:
"We are all of us in the gutter, but some of us are looking at
the stars"
-- Oscar Wilde
like so:
"We are all of us in the gutter, but some of us are looking at
the stars" -- Oscar Wilde
autoformat recognizes the quotation structure by matching the
following regular expression against the text component of each
paragraph:
/ \A(\s*) # leading whitespace for quotation (["']|``) # opening
quotemark (.*) # quotation (''|\2) # closing quotemark \s*?\n #
trailing whitespace after quotation (\1[ ]+) # leading
whitespace for attribution
# (must be indented more than
# quotation)
(--|-) # attribution introducer ([^\n]*?\n) # first
attribution line ((\5[^\n]*?$)*) # other attribution lines
# (indented no less than first line)
\s*\Z # optional whitespace to end of paragraph /xsm
When reformatted (see below), the indentation and the attribution structure will be preserved:
"We are all of us in the gutter, but some of us are looking at
the stars"
-- Oscar Wilde
Note that in the last example, autoformat broke the line at column
68, four characters earlier than it should have. It did so because, if
the full margin width had been used, the formatting would have left the
last two words by themselves on an oddly short last line:
"We are all of us in the gutter, but some of us are looking at
the stars"
This phenomenon is known as ``widowing'' and is heavily frowned upon in
typesetting circles. It looks ugly in plaintext too, so autoformat
avoids it by stealing extra words from earlier lines in a paragraph, so
as to leave enough for a reasonable last line. The heuristic used is
that final lines must be at least 10 characters long (though this number
may be adjusted by passing a widow => minlength argument to
autoformat).
If the last line is too short, the paragraph's right margin is reduced by one column, and the paragraph is reformatted. This process iterates until either the last line exceeds nine characters or the margins have been narrowed by 10% of their original separation. In the latter case, the reformatter gives up and uses its original formatting.
The autoformat subroutine also takes a named argument: {justify
=E<gt> I<type>}, which specifies how each paragraph is to be justified.
The options are: 'left' (the default), 'right', 'centre' (or
'center'), and 'full'. These act on the complete paragraph text
(but not on any quoters before that text). For example, with
'right' justification:
R3> Now is the Winter of our discontent made
R4> glorious Summer by this son of York. And all
R5> the clouds that lour'd upon our house In the
R6> deep bosom of the ocean buried.
Full justification is interesting in a fixed-width medium like plaintext because it usually results in uneven spacing between words. Typically, formatters provide this by distributing the extra spaces into the first available gaps of each line:
R7> Now is the Winter of our discontent made
R8> glorious Summer by this son of York. And all
R9> the clouds that lour'd upon our house In
R10> the deep bosom of the ocean buried.
This produces a rather jarring visual effect, so autoformat reverses
the strategy and inserts extra spaces at the end of lines:
R11> Now is the Winter of our discontent made
R12> glorious Summer by this son of York. And all
R13> the clouds that lour'd upon our house In
R14> the deep bosom of the ocean buried.
Most readers find this less disconcerting.
Even if explicit centring is not specified, autoformat will attempt
to automatically detect centred paragraphs and preserve their
justification. It does this by examining each line of the paragraph and
asking: ``if this line were part of a centred paragraph, where would the
centre line have been?''
The answer can be determined by adding the length of leading whitespace before the first word, plus half the length of the full set of words on the line. That is, for a single line:
$line =~ /^(\s*)(.*?)(\s*)$/ $centre =
length($1)+0.5*length($2);
By making the same estimate for every line, and then comparing the
estimates, it is possible to deduce whether all the lines are centred
with respect to the same axis of symmetry (with an allowance of
±1 to cater for the inevitable rounding when the centre
positions of even-length rows were originally computed). If a common
axis of symmetry is detected, autoformat assumes that the lines are
supposed to be centred, and switches to centre-justification mode for
that paragraph.
Note that this behaviour can to switched off entirely by setting the
"autocentre" argument false.
The autoformat subroutine can also optionally perform case
conversions on the text it processes. The {case => type}
argument allows the user to specify five different conversions:
'upper''lower''sentence'{case => 'sentence'}:
'POVERTY, MISERY, ETC. are the lot of the PhD candidate. alas!'
becomes:
'Poverty, misery, etc. are the lot of the PhD candidate. Alas!'
Note that autoformat is clever enough to recognize that the period
after abbreviations such as etc. is not a sentence terminator.
If the argument is specified as 'sentence ' (with one or more
trailing whitespace characters) those characters are used to replace the
single space that appears at the end of the sentence. For example,
autoformat($text, {case=>'sentence '}) would produce:
'Poverty, misery, etc. are the lot of the PhD candidate. Alas!'
'title''sentence' except that the first letter of
every word is capitalized:
'What I Did On My Summer Vacation In Monterey'
'highlight''title' except that trivial words are not
capitalized:
'What I Did on my Summer Vacation in Monterey'
You can select which paragraphs autoformat actually reformats (or,
rather, those it doesn't reformat) using the "ignore" flag.
For example:
# Reformat all paras except those containing "verbatim"...
print autoformat { all => 1, ignore => qr/verbatim/i }, $text;
# Reformat all paras except those less that 3 lines long...
print autoformat { all => 1, ignore => sub { tr/\n/\n/ < 3
} }, $text;
# Reformat all paras except those that are indented...
print autoformat { all => 1, ignore => qr/^\s/m }, $text;
# Reformat all paras except those that are indented (easier)...
print autoformat { all => 1, ignore => 'indented' }, $text;
The Text::Reform module
Damian Conway (damian@conway.org)
There are undoubtedly serious bugs lurking somewhere in code this funky :-) Bug reports and other feedback are most welcome.
Copyright (c) 1997-2000, Damian Conway. All Rights Reserved. This module is free software. It may be used, redistributed and/or modified under the terms of the Perl Artistic License (see http://www.perl.com/perl/misc/Artistic.html)
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Text::Autoformat - Automatic text wrapping and reformatting |