SYNOPSIS

par

[ help ] [ version ] [ Bopset ] [ Popset ] [ Qopset ] [ h[hang] ] [ p[prefix] ] [ r[repeat] ] [ s[suffix] ] [ T[Tab] ] [ w[width] ] [ b[body] ] [ c[cap] ] [ d[div] ] [ E[Err] ] [ e[expel] ] [ f[fit] ] [ g[guess] ] [ j[just] ] [ l[last] ] [ q[quote] ] [ R[Report] ] [ t[touch] ]

DESCRIPTION

par is a filter which copies its input to its output, changing all white characters (except newlines) to spaces, and reformatting each paragraph. Paragraphs are separated by protected, blank, and bodiless lines (see the TERMINOLOGY section for definitions), and optionally delimited by indentation (see the d option in the OPTIONS section).

Each output paragraph is generated from the corresponding input paragraph as follows:

1) An optional prefix and/or suffix is removed from each input line.

2) The remainder is divided into words (separated by spaces).

3) The words are joined into lines to make an eye-pleasing paragraph.

4) The prefixes and suffixes are reattached.

If there are suffixes, spaces are inserted before them so that they all end in the same column.

QUICK START

par is necessarily complex. For those who wish to use it immediately and understand it later, assign the PARINIT environment variable the following value:

rTbgqR B=.,?_A_a Q=_s>|

The spaces, question mark, greater-than sign, and vertical bar will probably have to be escaped or quoted to prevent your shell from interpreting them.

The documentation, though precise, is unfortunately not well-written for the end-user. Your best bet is probably to read quickly the DESCRIPTION, TERMINOLOGY, OPTIONS, and ENVIRONMENT sections, then read carefully the EXAMPLES section, referring back to the OPTIONS and TERMINOLOGY sections as needed.

For the "power user", a full understanding of par will require multiple readings of the TERMINOLOGY, OPTIONS, DETAILS, and EXAMPLES sections.

TERMINOLOGY

Miscellaneous terms:

charset syntax

A way of representing a set of characters as a string. The set includes exactly those characters which appear in the string, except that the underscore (_) is an escape character. Whenever it appears, it must begin one of the following escape sequences:

__ = an underscore

_s = a space

_b = a backslash (\)

_q = a single quote (')

_Q = a double quote ()

_A = all upper case letters

_a = all lower case letters

_0 = all decimal digits

_xhh = the character represented by the two hexadecimal digits hh (which may be upper or lower case)

The NUL character must not appear in the string, but it may be included in the set with the _x00 sequence.

error

A condition which causes par to abort. See the DIAGNOSTICS section.

IP

Input paragraph.

OP

Output paragraph.

parameter

A symbol which may take on unsigned integral values. There are several parameters whose values affect the behavior of par. Parameters can be assigned values using command line options.

Types of characters:

alphanumeric character

An upper case letter, lower case letter, or decimal digit.

body character

A member of the set of characters defined by the PARBODY environment variable (see the ENVIRONMENT section) and/or the B option (see the OPTIONS section).

protective character

A member of the set of characters defined by the PARPROTECT environment variable and/or the P option.

quote character

A member of the set of characters defined by the PARQUOTE environment variable and/or the Q option.

terminal character

A period, question mark, exclamation point, or colon.

white character

A space, formfeed, newline, carriage return, tab, or vertical tab.

Functions:

comprelen

Given a non-empty sequence S of lines, let c be their longest common prefix. If the parameter body is 0, place a divider just after the leading non-body characters in c (at the beginning if there are none). If body is 1, place the divider just after the last non-space non-body character in c (at the beginning if there is none), then advance the divider over any immediately following spaces. The comprelen of S is the number of characters preceding the divider.

comsuflen

Given a non-empty sequence S of lines, let p be the comprelen of S. Let T be the set of lines which result from stripping the first p characters from each line in S. Let c be the longest common suffix of the lines in T. If body is 0, place a divider just before the trailing non-body characters in c (at the end if there are none), then advance the divider over all but the last of any immediately following spaces. If body is 1, place the divider just before the first non-space non-body character, then back up the divider over one immediately preceding space if there is one. The comsuflen of S is the number of characters following the divider.

fallback prelen (suflen)

The fallback prelen (suflen) of an IP is: the comprelen (comsuflen) of the IP, if the IP contains at least two lines; otherwise, the comprelen (comsuflen) of the block containing the IP, if the block contains at least two lines; otherwise, the length of the longer of the prefixes (suffixes) of the bodiless lines just above and below the block, if the segment containing the block has any bodiless lines; otherwise, 0. (See below for the definitions of block, segment, and bodiless line.)

augmented fallback prelen

Let fp be the fallback prelen of an IP. If the IP contains more than one line, or if quote is 0, then the augmented fallback prelen of the IP is simply fp. Otherwise, it is fp plus the number of quote characters immediately following the first fp characters of the line.

quoteprefix

The quoteprefix of a line is the longest string of quote characters appearing at the beginning of the line, after this string has been stripped of any trailing spaces.

Types of lines:

blank line

An empty line, or a line whose first character is not protective and which contains only spaces.

protected line

An input line whose first character is protective.

bodiless line

A line which is order k bodiless for some k.

order k bodiless line

There is no such thing as an order 0 bodiless line. Suppose S is a a contiguous subsequence of a segment (see below) containing at least two lines, containing no order k-1 bodiless lines, bounded above and below by order k-1 bodiless lines and/or the beginning/end of the segment. Let p and s be the comprelen and comsuflen of S. Any member of S which, if stripped of its first p and last s characters, would be blank (or, if the parameter repeat is non-zero, would consist of the same character repeated at least repeat times), is order k bodiless. The first p characters of the bodiless line comprise its prefix; the last s characters comprise its suffix. The character which repeats in the middle is called its repeat character. If the middle is empty, the space is taken to be its repeat character.

vacant line

A bodiless line whose repeat character is the space.

superfluous line

Only blank and vacant lines may be superfluous. If contiguous vacant lines lie at the beginning or end of a segment, they are all superfluous. But if they lie between two non-vacant lines within a segment, then all are superfluous except one---the one which contains the fewest non-spaces. In case of a tie, the first of the tied lines is chosen. Similarly, if contiguous blank lines lie outside of any segments at the beginning or end of the input, they are all superfluous. But if they lie between two segments and/or protected lines, then all are superfluous except the first.

Groups of lines:

segment

A contiguous sequence of input lines containing no protected or blank lines, bounded above and below by protected lines, blank lines, and/or the beginning/end of the input.

block

A contiguous subsequence of a segment containing no bodiless lines, bounded above and below by bodiless lines and/or the beginning/end of the segment.

Types of words:

capitalized word

If the parameter cap is 0, a capitalized word is one which contains at least one alphanumeric character, whose first alphanumeric character is not a lower case letter. If cap is 1, every word is considered a capitalized word. (See the c option in the OPTIONS section.)

curious word

A word which contains a terminal character c such that there are no alphanumeric characters in the word after c, but there is at least one alphanumeric character in the word before c.

OPTIONS

Any command line argument may begin with one minus sign (-) which is ignored. Generally, more than one option may appear in a single command line argument, but there are exceptions: The help, version, B, P, and Q options must have whole arguments all to themselves.

help

Causes all remaining arguments to be ignored. No input is read. A usage message is printed on the output briefly describing the options used by par.

version

Causes all remaining arguments to be ignored. No input is read. "par 1.52" is printed on the output. Of course, this will change in future releases of Par.

Bopset

op is a single character, either an equal sign (=), a plus sign (+), or a minus sign (-), and set is a string using charset syntax. If op is an equal sign, the set of body characters is set to the character set defined by set. If op is a plus/minus sign, the characters in the set defined by set are added/removed to/from the existing set of body characters defined by the PARBODY environment variable and any previous B options. It is okay to add characters that are already in the set or to remove characters that are not in the set.

Popset

Just like the B option, except that it applies to the set of protective characters.

Qopset

Just like the B option, except that it applies to the set of quote characters.

All remaining options are used to set values of parameters. Values set by command line options hold for all paragraphs. Unset parameters are given default values. Any parameters whose default values depend on the IP (namely prefix and suffix), if left unset, are recomputed separately for each paragraph.

The approximate role of each variable is described here. See the DETAILS section for the rest of the story.

The first six parameters, hang, prefix, repeat, suffix, Tab, and width, may be set to any unsigned decimal integer less than 10000.

h[hang]

Mainly affects the default values of prefix and suffix. Defaults to 0. If the h option is given without a number, the value 1 is inferred. (See also the p and s options.)

p[prefix]

The first prefix characters of each line of the OP are copied from the first prefix characters of the corresponding line of the IP. If there are more than hang+1 lines in the IP, the default value is the comprelen of all the lines in the IP except the first hang of them. Otherwise, the default value is the augmented fallback prelen of the IP. If the p option is given without a number, prefix is unset, even if it had been set earlier. (See also the h and q options.)

r[repeat]

If repeat is non-zero, bodiless lines have the number of instances of their repeat characters increased or decreased until the length of the line is width. The exact value of repeat affects the definition of bodiless line. Defaults to 0. If the r option is given without a number, the value 3 is inferred. (See also the w option.)

s[suffix]

The last suffix characters of each line of the OP are copied from the last suffix characters of the corresponding line of the IP. If there are more than hang+1 lines in the IP, the default value is the comsuflen of all the lines of the IP except the first hang of them. Otherwise, the default value is the fallback suflen of the IP. If the s option is given without a number, suffix is unset, even if it had been set earlier. (See also the h option.)

T[Tab]

Tab characters in the input are expanded to spaces, assuming tab stops every Tab columns. Must not be 0. Defaults to 1. If the T option is given without a number, the value 8 is inferred.

w[width]

No line in the OP may contain more than width characters, not including the trailing newlines. Defaults to 72. If the w option is given without a number, the value 79 is inferred.

The remaining thirteen parameters, body, cap, div, Err, expel, fit, guess, invis, just, last, quote, Report, and touch, may be set to either 0 or 1. If the number is absent in the option, the value 1 is inferred.

b[body]

If body is 1, prefixes may not contain any trailing body characters, and suffixes may not contain any leading body characters. (Actually, the situation is complicated by space characters. See comprelen and comsuflen in the Terminology section.) If body is 0, prefixes and suffixes may not contain any body characters at all. Defaults to 0.

c[cap]

If cap is 1, all words are considered capitalized. This currently affects only the application of the g option. Defaults to 0.

d[div]

If div is 0, each block becomes an IP. If div is 1, each block is subdivided into IPs as follows: Let p be the comprelen of the block. Let a line's status be 1 if its (p+1)st character is a space, 0 otherwise. Every line in the block whose status is the same as the status of the first line will begin a new paragraph. Defaults to 0.

E[Err]

If Err is 1, messages to the user (caused by the help and version options, or by errors) are sent to the error stream instead of the output stream. Defaults to 0.

e[expel]

If expel is 1, superfluous lines are withheld from the output. Defaults to 0.

f[fit]

If fit is 1 and just is 0, par tries to make the lines in the OP as nearly the same length as possible, even if it means making the OP narrower. Defaults to 0. (See also the j option.)

g[guess]

If guess is 1, then when par is choosing line breaks, whenever it encounters a curious word followed by a capitalized word, it takes one of two special actions. If the two words are separated by a single space in the input, they will be merged into one word with an embedded non-breaking space. If the two words are separated by more than one space, or by a line break, par will insure that they are separated by two spaces, or by a line break, in the output. Defaults to 0.

i[invis]

If invis is 1, then vacant lines inserted because quote is 1 are invisible; that is, they are not output. If quote is 0, invis has no effect. Defaults to 0. (See also the q option.)

j[just]

If just is 1, par justifies the OP, inserting spaces between words so that all lines in the OP have length width (except the last, if last is 0). Defaults to 0. (See also the w, l, and f options.)

l[last]

If last is 1, par tries to make the last line of the OP about the same length as the others. Defaults to 0.

q[quote]

If quote is 1, then before each segment is scanned for bodiless lines, par supplies vacant lines between different quotation nesting levels as follows: For each pair of adjacent lines in the segment, (scanned from the top down) which have different quoteprefixes, one of two actions is taken. If invis is 0, and either line consists entirely of quote characters and spaces (or is empty), that line is truncated to the longest common prefix of the two lines (both are truncated if both qualify). Otherwise, a line consisting of the longest common prefix of the two lines is inserted between them. quote also affects the default value of prefix. Defaults to 0. (See also the p and i options.)

R[Report]

If Report is 1, it is considered an error for an input word to contain more than L = (width - prefix - suffix) characters. Otherwise, such words are chopped after each Lth character into shorter words. Defaults to 0.

t[touch]

Has no effect if suffix is 0 or just is 1. Otherwise, if touch is 0, all lines in the OP have length width. If touch is 1, the length of the lines is decreased until the suffixes touch the body of the OP. Defaults to the logical OR of fit and last. (See also the s, j, w, f, and l options.)

If an argument begins with a number, that number is assumed to belong to a p option if it is 8 or less, and to a w option otherwise.

If the value of any parameter is set more than once, the last value is used. When unset parameters are assigned default values, hang and quote are assigned before prefix, and fit and last are assigned before touch (because of the dependencies).

It is an error if width <= prefix + suffix.

DETAILS

Lines are terminated by newline characters, but the newlines are not considered to be included in the lines. If the last character of the input is a non-newline, a newline will be inferred immediately after it (but if the input is empty, no newline will be inferred; the number of input lines will be 0). Thus, the input can always be viewed as a sequence of lines.

Protected lines are copied unchanged from the input to the output. All other input lines, as they are read, have any NUL characters removed, and every white character (except newlines) turned into a space. Actually, each tab character is turned into Tab - (n % Tab) spaces, where n is the number of characters preceding the tab character on the line (evaluated after earlier tab characters have been expanded).

Blank lines in the input are transformed into empty lines in the output.

If repeat is 0, all bodiless lines are vacant, and they are all simply stripped of trailing spaces before being output. If repeat is not 0, only vacant lines whose suffixes have length 0 are treated that way; other bodiless lines have the number of instances of their repeat characters increased or decreased until the length of the line is width.

If expel is 1, superfluous lines are not output. If quote and invis are both 1, there may be invisible lines; they are not output.

The input is divided into segments, which are divided into blocks, which are divided into IPs. The exact process depends on the values of quote and div (see q and d in the OPTIONS section). The remainder of this section describes the process which is applied independently to each IP to construct the corresponding OP.

After the values of the parameters are determined (see the OPTIONS section), the first prefix characters and the last suffix characters of each input line are removed and remembered. It is an error for any line to contain fewer than prefix + suffix characters.

The remaining text is treated as a sequence of characters, not lines. The text is broken into words, which are separated by spaces. That is, a word is a maximal sub-sequence of non-spaces. If guess is 1, some words might be merged (see g in the OPTIONS section). The first word includes any spaces that precede it on the same line.

Let L = width - prefix - suffix.

If Report is 0, some words may get chopped up at this point (see R in the OPTIONS section).

The words are reassembled, preserving their order, into lines. If just is 0, adjacent words within a line are separated by a single space, (or sometimes two if guess is 1), and line breaks are chosen so that the paragraph satisfies the following properties:

1) No line contains more than L characters.

2) If fit is 1, the difference between the lengths of the shortest and longest lines is as small as possible.

3) The shortest line is as long as possible, subject to properties 1 and 2.

4) Let target be L if fit is 0, or the length of the longest line if fit is 1. The sum of the squares of the differences between target and the lengths of the lines is as small as possible, subject to properties 1, 2, and 3.

If last is 0, the last line does not count as a line for the purposes of properties 2, 3, and 4 above.

If all the words fit on a single line, the properties as worded above don't make much sense. In that case, no line breaks are inserted.

If just is 1, adjacent words within a line are separated by one space (or sometimes two if guess is 1) plus zero or more extra spaces. The value of fit is disregarded, and line breaks are chosen so that the paragraph satisfies the following properties:

1) Every line contains exactly L characters.

2) The largest inter-word gap is as small as possible, subject to property 1. (An inter-word gap consists only of the extra spaces, not the regular spaces.)

3) The sum of the squares of the lengths of the inter-word gaps is as small as possible, subject to properties 1 and 2.

If last is 0, the last line does not count as a line for the purposes of property 1, and it does not require or contain any extra spaces.

Extra spaces are distributed as uniformly as possible among the inter-word gaps in each line.

In a justified paragraph, every line must contain at least two words, but that's not always possible to accomplish. If the paragraph cannot be justified, it is considered an error.

If the number of lines in the resulting paragraph is less than hang, empty lines are added at the end to bring the number of lines up to hang.

If just is 0 and touch is 1, L is changed to be the length of the longest line.

If suffix is not 0, each line is padded at the end with spaces to bring its length up to L.

To each line is prepended prefix characters. Let n be the number of lines in the IP, let afp be the augmented fallback prelen of the IP, and let fs be the fallback suflen of the IP. The characters which are prepended to the ith line are chosen as follows:

1) If i <= n, the characters are copied from the ones that were removed from the beginning of the nth input line.

2) If i > n > hang, the characters are copied from the ones that were removed from the beginning of the last input line.

3) If i > n and n <= hang, the first min(afp,prefix) of the characters are copied from the ones that were removed from the beginning of the last input line, and the rest are all spaces.

Then to each line is appended suffix characters. The characters which are appended to the ith line are chosen as follows:

1) If i <= n, the characters are copied from the ones that were removed from the end of the nth input line.

2) If i > n > hang, the characters are copied from the ones that were removed from the end of the last input line.

3) If i > n and n <= hang, the first min(fs,suffix) of the characters are copied from the ones that were removed from the beginning of the last input line, and the rest are all spaces.

Finally, the lines are printed to the output as the OP.

DIAGNOSTICS

If there are no errors, par returns EXIT_SUCCESS (see <stdlib.h>).

If there is an error, an error message will be printed to the output, and par will return EXIT_FAILURE. If the error is local to a single paragraph, the preceding paragraphs will have been output before the error was detected. Line numbers in error messages are local to the IP in which the error occurred. All error messages begin with "par error:" on a line by itself. Error messages concerning command line or environment variable syntax are accompanied by the same usage message that the help option produces.

Unless the option E is set, trying to print an error message would be futile if an error resulted from an output function, so par doesn't bother doing any error checking on output functions if E is 0.

EXAMPLES

The superiority of par's dynamic programming algorithm over a greedy algorithm (such as the one used by fmt) can be seen in the following example:

Original paragraph (note that each line begins with 8 spaces):

        We the people of the United States,
        in order to form a more perfect union,
        establish justice,
        insure domestic tranquility,
        provide for the common defense,
        promote the general welfare,
        and secure the blessing of liberty
        to ourselves and our posterity,
        do ordain and establish the Constitution
        of the United States of America.

After a greedy algorithm with width = 39:

        We the people of the United
        States, in order to form a more
        perfect union, establish
        justice, insure domestic
        tranquility, provide for the
        common defense, promote the
        general welfare, and secure the
        blessing of liberty to
        ourselves and our posterity, do
        ordain and establish the
        Constitution of the United
        States of America.

After "par 39":

        We the people of the United
        States, in order to form a
        more perfect union, establish
        justice, insure domestic
        tranquility, provide for the
        common defense, promote the
        general welfare, and secure
        the blessing of liberty to
        ourselves and our posterity,
        do ordain and establish the
        Constitution of the United
        States of America.

The line breaks chosen by par are clearly more eye-pleasing.

par is most useful in conjunction with the text-filtering features of an editor, such as the ! commands of vi. You may wish to add the following lines to your .exrc file:

        " use Bourne shell for speed:
        set shell=/bin/sh
        "
        " reformat paragraph with no arguments:
        map ** {!}par^M}
        "
        " reformat paragraph with arguments:
        map *^V  {!}par

Note that the leading spaces must be removed, and that what is shown as ^M and ^V really need to be ctrl-M and ctrl-V. Also note that the last map command contains two spaces following the ctrl-V, plus one at the end of the line.

To reformat a simple paragraph delimited by blank lines in vi, you can put the cursor anywhere in it and type "**" (star star). If you need to supply arguments to par, you can type "* " (star space) instead, then type the arguments.

The rest of this section is a series of before-and-after pictures showing some typical uses of par. In all cases, no environment variables are set.

Before:

        /*   We the people of the United States, */
        /* in order to form a more perfect union, */
        /* establish justice, */
        /* insure domestic tranquility, */
        /* provide for the common defense, */
        /* promote the general welfare, */
        /* and secure the blessing of liberty */
        /* to ourselves and our posterity, */
        /* do ordain and establish the Constitution */
        /* of the United States of America. */

After "par 59":

        /*   We the people of the United States, in      */
        /* order to form a more perfect union, establish */
        /* justice, insure domestic tranquility, provide */
        /* for the common defense, promote the general   */
        /* welfare, and secure the blessing of liberty   */
        /* to ourselves and our posterity, do ordain     */
        /* and establish the Constitution of the United  */
        /* States of America.                            */

Or after "par 59f":

        /*   We the people of the United States,  */
        /* in order to form a more perfect union, */
        /* establish justice, insure domestic     */
        /* tranquility, provide for the common    */
        /* defense, promote the general welfare,  */
        /* and secure the blessing of liberty to  */
        /* ourselves and our posterity, do ordain */
        /* and establish the Constitution of the  */
        /* United States of America.              */

Or after "par 59l":

        /*   We the people of the United States, in      */
        /* order to form a more perfect union, establish */
        /* justice, insure domestic tranquility,         */
        /* provide for the common defense, promote       */
        /* the general welfare, and secure the           */
        /* blessing of liberty to ourselves and our      */
        /* posterity, do ordain and establish the        */
        /* Constitution of the United States of America. */

Or after "par 59lf":

        /*   We the people of the United States,  */
        /* in order to form a more perfect union, */
        /* establish justice, insure domestic     */
        /* tranquility, provide for the common    */
        /* defense, promote the general welfare,  */
        /* and secure the blessing of liberty     */
        /* to ourselves and our posterity, do     */
        /* ordain and establish the Constitution  */
        /* of the United States of America.       */

Or after "par 59lft0":

        /*   We the people of the United States,         */
        /* in order to form a more perfect union,        */
        /* establish justice, insure domestic            */
        /* tranquility, provide for the common           */
        /* defense, promote the general welfare,         */
        /* and secure the blessing of liberty            */
        /* to ourselves and our posterity, do            */
        /* ordain and establish the Constitution         */
        /* of the United States of America.              */

Or after "par 59j":

        /*   We  the people  of  the  United States,  in */
        /* order to form a more perfect union, establish */
        /* justice, insure domestic tranquility, provide */
        /* for the  common defense, promote  the general */
        /* welfare, and  secure the blessing  of liberty */
        /* to ourselves and our posterity, do ordain and */
        /* establish  the  Constitution  of  the  United */
        /* States of America.                            */

Or after "par 59jl":

        /*   We  the   people  of  the   United  States, */
        /* in   order    to   form   a    more   perfect */
        /* union,  establish  justice,  insure  domestic */
        /* tranquility, provide for  the common defense, */
        /* promote  the  general   welfare,  and  secure */
        /* the  blessing  of  liberty to  ourselves  and */
        /* our  posterity, do  ordain and  establish the */
        /* Constitution of the United States of America. */

Before:

        Preamble      We the people of the United States,
        to the US     in order to form
        Constitution  a more perfect union,
                      establish justice,
                      insure domestic tranquility,
                      provide for the common defense,
                      promote the general welfare,
                      and secure the blessing of liberty
                      to ourselves and our posterity,
                      do ordain and establish
                      the Constitution
                      of the United States of America.

After "par 52h3":

        Preamble      We the people of the United
        to the US     States, in order to form a
        Constitution  more perfect union, establish
                      justice, insure domestic
                      tranquility, provide for the
                      common defense, promote the
                      general welfare, and secure
                      the blessing of liberty to
                      ourselves and our posterity,
                      do ordain and establish the
                      Constitution of the United
                      States of America.

Before:

         1  We the people of the United States,
         2  in order to form a more perfect union,
         3  establish justice,
         4  insure domestic tranquility,
         5  provide for the common defense,
         6  promote the general welfare,
         7  and secure the blessing of liberty
         8  to ourselves and our posterity,
         9  do ordain and establish the Constitution
        10  of the United States of America.

After "par 59p12l":

         1  We the people of the United States, in order to
         2  form a more perfect union, establish justice,
         3  insure domestic tranquility, provide for the
         4  common defense, promote the general welfare,
         5  and secure the blessing of liberty to ourselves
         6  and our posterity, do ordain and establish the
         7  Constitution of the United States of America.

Before:

        > > We the people
        > > of the United States,
        > > in order to form a more perfect union,
        > > establish justice,
        > > ensure domestic tranquility,
        > > provide for the common defense,
        >
        > Promote the general welfare,
        > and secure the blessing of liberty
        > to ourselves and our posterity,
        > do ordain and establish
        > the Constitution of the United States of America.

After "par 52":

        > > We the people of the United States, in
        > > order to form a more perfect union,
        > > establish justice, ensure domestic
        > > tranquility, provide for the common
        > > defense,
        >
        > Promote the general welfare, and secure
        > the blessing of liberty to ourselves and
        > our posterity, do ordain and establish
        > the Constitution of the United States of
        > America.

Before:

        >   We the people
        > of the United States,
        > in order to form a more perfect union,
        > establish justice,
        > ensure domestic tranquility,
        > provide for the common defense,
        >   Promote the general welfare,
        > and secure the blessing of liberty
        > to ourselves and our posterity,
        > do ordain and establish
        > the Constitution of the United States of America.

After "par 52d":

        >   We the people of the United States,
        > in order to form a more perfect union,
        > establish justice, ensure domestic
        > tranquility, provide for the common
        > defense,
        >   Promote the general welfare, and secure
        > the blessing of liberty to ourselves and
        > our posterity, do ordain and establish
        > the Constitution of the United States of
        > America.

Before:

        # 1. We the people of the United States.
        # 2. In order to form a more perfect union.
        # 3. Establish justice, ensure domestic
        #    tranquility.
        # 4. Provide for the common defense
        # 5. Promote the general welfare.
        # 6. And secure the blessing of liberty
        #    to ourselves and our posterity.
        # 7. Do ordain and establish the Constitution.
        # 8. Of the United States of America.

After "par 37p13dh":

        # 1. We the people of the
        #    United States.
        # 2. In order to form a more
        #    perfect union.
        # 3. Establish justice,
        #    ensure domestic
        #    tranquility.
        # 4. Provide for the common
        #    defense
        # 5. Promote the general
        #    welfare.
        # 6. And secure the blessing
        #    of liberty to ourselves
        #    and our posterity.
        # 7. Do ordain and establish
        #    the Constitution.
        # 8. Of the United States of
        #    America.

Before:

        /*****************************************/
        /*   We the people of the United States, */
        /* in order to form a more perfect union, */
        /* establish justice, insure domestic    */
        /* tranquility,                          */
        /*                                       */
        /*                                       */
        /*   [ provide for the common defense, ] */
        /*   [ promote the general welfare,    ] */
        /*   [ and secure the blessing of liberty ] */
        /*   [ to ourselves and our posterity, ] */
        /*   [                                 ] */
        /*                                       */
        /* do ordain and establish the Constitution */
        /* of the United States of America.       */
        /******************************************/

After "par 42r":

        /********************************/
        /*   We the people of the       */
        /* United States, in order to   */
        /* form a more perfect union,   */
        /* establish justice, insure    */
        /* domestic tranquility,        */
        /*                              */
        /*                              */
        /*   [ provide for the common ] */
        /*   [ defense, promote the   ] */
        /*   [ general welfare, and   ] */
        /*   [ secure the blessing of ] */
        /*   [ liberty to ourselves   ] */
        /*   [ and our posterity,     ] */
        /*   [                        ] */
        /*                              */
        /* do ordain and establish the  */
        /* Constitution of the United   */
        /* States of America.           */
        /********************************/

Or after "par 42re":

        /********************************/
        /*   We the people of the       */
        /* United States, in order to   */
        /* form a more perfect union,   */
        /* establish justice, insure    */
        /* domestic tranquility,        */
        /*                              */
        /*   [ provide for the common ] */
        /*   [ defense, promote the   ] */
        /*   [ general welfare, and   ] */
        /*   [ secure the blessing of ] */
        /*   [ liberty to ourselves   ] */
        /*   [ and our posterity,     ] */
        /*                              */
        /* do ordain and establish the  */
        /* Constitution of the United   */
        /* States of America.           */
        /********************************/

Before:

        Joe Public writes:
        > Jane Doe writes:
        > >
        > >
        > > I can't find the source for uncompress.
        > Oh no, not again!!!
        >
        >
        > Isn't there a FAQ for this?
        >
        >
        That wasn't very helpful, Joe. Jane,
        just make a link from uncompress to compress.

After "par 40q":

        Joe Public writes:
        > Jane Doe writes:
        >
        >
        > > I can't find the source for
        > > uncompress.
        >
        > Oh no, not again!!!
        >
        >
        > Isn't there a FAQ for this?
        >
        That wasn't very helpful, Joe.
        Jane, just make a link from
        uncompress to compress.

Or after "par 40qe":

        Joe Public writes:
        > Jane Doe writes:
        >
        > > I can't find the source for
        > > uncompress.
        >
        > Oh no, not again!!!
        >
        > Isn't there a FAQ for this?
        That wasn't very helpful, Joe.
        Jane, just make a link from
        uncompress to compress.

Or after "par 40qi":

        Joe Public writes:
        > Jane Doe writes:
        > >
        > >
        > > I can't find the source for
        > > uncompress.
        > Oh no, not again!!!
        >
        >
        > Isn't there a FAQ for this?
        >
        >
        That wasn't very helpful, Joe.
        Jane, just make a link from
        uncompress to compress.

Or after "par 40qie":

        Joe Public writes:
        > Jane Doe writes:
        > > I can't find the source for
        > > uncompress.
        > Oh no, not again!!!
        >
        > Isn't there a FAQ for this?
        That wasn't very helpful, Joe.
        Jane, just make a link from
        uncompress to compress.

Before:

        I sure hope there's still room
        in Dr. Jones' section of archaeology.
        I've heard he's the bestest.  [sic]

After "par 50g":

        I sure hope there's still room in
        Dr. Jones' section of archaeology.  I've
        heard he's the bestest. [sic]

Or after "par 50gc":

        I sure hope there's still room in
        Dr. Jones' section of archaeology.  I've
        heard he's the bestest.  [sic]

Before:

        John writes:
        : Mary writes:
        : + Anastasia writes:
        : + > Hi all!
        : + Hi Ana!
        : Hi Ana & Mary!
        Please unsubscribe me from alt.hello.

After "par Q+:+ q":

        John writes:
        : Mary writes:
        :
        : + Anastasia writes:
        : +
        : + > Hi all!
        : +
        : + Hi Ana!
        :
        : Hi Ana & Mary!
        Please unsubscribe me from alt.hello.

Before:

        amc> The b option was added primarily to deal with
        amc> this new style of quotation
        amc> which became popular after Par 1.41 was released.
        amc>
        amc> Par still pays attention to body characters.
        amc> Par should not mistake "Par" for part of the prefix.
        amc> Par should not mistake "." for a suffix.

After "par B=._A_a 50bg":

        amc> The b option was added primarily to
        amc> deal with this new style of quotation
        amc> which became popular after Par 1.41
        amc> was released.
        amc>
        amc> Par still pays attention to body
        amc> characters.  Par should not mistake
        amc> "Par" for part of the prefix.  Par
        amc> should not mistake "." for a suffix.

LIMITATIONS

The guess feature guesses wrong in cases like the following:

        I calc'd the approx.
        Fermi level to 3 sig. digits.

With guess = 1, par will incorrectly assume that "approx." ends a sentence. If the input were:

        I calc'd the approx. Fermi
        level to 3 sig. digits.

then par would refuse to put a line break between "approx." and "Fermi" in the output, mainly to avoid creating the first situation (in case the paragraph were to be fed back through par again). This non-breaking space policy does come in handy for cases like "Mr. Johnson" and "Jan. 1", though.

The guess feature only goes one way. par can preserve wide sentence breaks in a paragraph, or remove them, but it can't insert them if they aren't already in the input.

If you use tabs, you may not like the way par handles (or doesn't handle) them. It expands them into spaces. I didn't let par output tabs because tabs don't make sense. Not everyone's terminal has the same tab settings, so text files containing tabs are sometimes mangled. In fact, almost every text file containing tabs gets mangled when something is inserted at the beginning of each line (when quoting e-mail or commenting out a section of a shell script, for example), making them a pain to edit. In my opinion, the world would be a nicer place if everyone stopped using tabs, so I'm doing my part by not letting par output them. (Thanks to Eric Stuebe for showing me the light about tabs.)

There is currently no way for the length of the output prefix to differ from the length of the input prefix. Ditto for the suffix. I may consider adding this capability in a future release, but right now I'm not sure how I'd want it to work.

APOLOGIES

Par began in July 1993 as a small program designed to do one narrow task: reformat a single paragraph that might have a border on either side. It was pretty clean back then. Over the next three months, it very rapidly expanded to handle multiple paragraphs, offer more options, and take better guesses, at the cost of becoming extremely complex, and very unclean. It is nowhere near the optimal design for the larger task it now tries to address. Its only redeeming features are that it is extremely useful (I find it indispensable), extremely portable, and very stable (between the release of version 1.41 on 1993-Oct-31 and the release of version 1.52 on 2001-Apr-29, no incorrect behavior was reported).

Back in 1993 I had very little experience at writing documentation for users, so the documentation for Par became rather nightmarish. There is no separation between how-it-works (which is painfully complex) and how-to-use-it (which is fairly simple, if you can ever figure it out).

Someday I ought to reexamine the problem, and redesign a new, clean solution from scratch. I don't know when I might get enough free time to start on such a project. Text files may be obsolete by then.