PP - Pascal Prettyprinting Program

			      11 October 1984

			      - Jon Hueras and
			         Henry Ledgard
			      - Rick L. Marcus


What PP Does
------------

     PP takes as input a Pascal program or program fragment and reformats it
according  to  a  standard  set  of prettyprinting rules.  The prettyprinted
program is given as output.  PP  makes  no  attempt  to  detect  or  correct
syntactic  errors  in your program.  However, syntactic errors may result in
erroneous prettyprinting.

     PP  differs from some other prettyprinting programs in that it does not
reformat your  program  "right  down  to  every  last  semicolon."   Such  a
philosophy  requires formatting everything in a rigid fashion which is bound
to be displeasing, or else it must provide you  with  a  voluminous  set  of
"options."   Furthermore,  such a scheme must do full syntax analysis of the
program which means that it must be completely written and  compilable.   If
you  wish to prettyprint a program still under development, then you are out
of luck.

     PP,  on  the  other hand, implements a strategy which states that it is
not necessary to impose more than a "minimum" set of restrictions,  and  the
prettyprinter  should  yield  to  your  discretion  beyond this minimum.  PP
preserves blank lines and extra spaces you insert in the program  as  input,
besides  adding  blank  lines  and  extra  spaces according to the rules for
prettyprinting given below.


General prettyprinting rules:

1.	All statements and declarations begin on separate lines.

2.	No  input  line  may  be longer than 80 characters.  Any output line
        longer than 80 characters is continued on a separate line.

3.	The  keywords  "BEGIN",  "END", "REPEAT", and "RECORD" are forced to
        stand on lines by themselves (or  possibly  followed  by  supporting
        comments).   In  addition,  the  "UNTIL"  clause  of  "REPEAT-UNTIL"
        statement is forced to start on a new line.

4.	A  blank  line is forced before the keywords "PROGRAM", "PROCEDURE",
        "FUNCTION", "LABEL", "CONST", "TYPE", and "VAR".

5.	A  space  is  forced  before  and  after  the  symbols ":=" and "=".
        Additionally, a space is forced after the  symbol  ":".   Note  that
        only  "="s  in  declarations  are formatted; "="s in expressions are
        ignored.

6.	Spaces  and blank lines already in your program are preserved by PP,
        which adds (but does not subtract) blank lines and spaces.  You  can
        improve the readability of your programs by taking advantage of this
        feature.   However,  this  feature also means that you may sometimes
        have to manually de-indent (in your editor)  after  block  structure
        changes.

Indentation rules:

1.	The  body  of  a  declaration is indented from the "LABEL", "CONST",
        "TYPE", or "VAR" keyword which heads it.

2.	The  bodies  of  "BEGIN-END",  "REPEAT-UNTIL",  "WHILE", "WITH", and
        "CASE" statements, as well as  "RECORD-END"  structures  and  "CASE"
        variants (to one level) are indented from keywords which head them.

3.	An "IF-THEN-ELSE" statement is indented as follows:

               IF <expression>
                  THEN <statement>
                  ELSE <statement>



When to Use PP
--------------

     PP  is  especially  useful  to  reformat  a  Pascal  program or program
fragment that you have typed without regard to formatting (such as  entering
every  line  left-justified  to save time).  Because the program need not be
syntactically correct, PP provides the fastest means  of  obtaining  a  more
readable version of your program.

     PP  is  best  used to prettyprint a Pascal program already on a file or
punched on cards.  PP changes neither the cards nor the file used as  input.
Prettyprinting  a  program  line-by-line  as  it is entered at a terminal is
considerably less useful.


How to Use PP
-------------

     Type  "PP" at the system command level followed by the old and new file
names.  If the new file already  exists,  it  will  be  overwritten  without
warning.   If  the  wrong  number  of  file names are given, PP will print a
message reminding the user of the correct system call.

Examples
--------

     1.  Reformat a program called "prog1.pas" under CP/M:

            PP prog1.pas prog1.new       ;  reformat a program
            TYPE prog1.new               ;  check that it is correct
            ERA prog1.pas                ;  delete the old version
            REN prog1.pas=prog1.new      ;  rename the new version

     2.  Reformat the same program under MS-DOS:

            PP prog1.pas prog1.new
            TYPE prog1.new
            ERASE prog1.pas
            RENAME prog1.new prog1.pas

     3.  Preview PP's output before writing to a file:

            PP prog.pas con:            ;  on CP/M
            PP prog.pas con             ;  on MS-DOS

     4.  Remind oneself how to use PP:

            PP


History
-------

     PP  prettyprints  a  Pascal program or program fragment given as input.
It was originally named PRETTYPRINT and was written in Pascal by Jon  Hueras
and  Henry Ledgard, University Computing Center and Computer and Information
Science Dept., University of Massachusetts  at  Amherst,  in  August,  1976.
(See  "An  Automatic Formatting Program for Pascal", by Jon Hueras and Henry
Ledgard, Pascal Newsletter #6, page 70, November, 1976.)

     Small  corrections  were  made to PRETTYPRINT by Charles Fischer, Dept.
of Computer Science, University of Wisconsin, Madison, in 1977.  PRETTYPRINT
was modified for CDC-6000 Pascal by Rick  L.   Marcus,  University  Computer
Center, University of Minnesota, in September, 1978, and was renamed PRETTY.
Marcus also wrote this documentation.

     Peter  Grogono  adapted  PRETTYPRINT  to CP/M, using Pascal/Z.  He also
made several modifications and  renamed  it  PP  (date  unknown).   In  1984
Willett Kempton adapted the Pascal/Z version to Turbo Pascal, which required
only  minor  mods.   The  Turbo  version  uses  a  portable argument library
"ARGLIB.PAS" to get file names, which makes it easier to adapt PP  to  other
Pascal  systems.   The  Turbo  version  has  been  tested  under CP/M-80 and
CP/M-86,  and  is  believed  to  work  without  modification   (other   than
recompilation)  under MS-DOS.  Kempton also adapted this documentation, from
the CDC version, to apply to the microcomputer version.sion  has  been  tested  under CP/M-80 and