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PRETTY: Pascal PrettyPrinting Program
January 1979
INTRODUCTION
The PRETTY program takes Pascal source files and inserts spaces
and carriage returns so as to make them conform to certain formatting
conventions. PRETTY retains any spaces or carriage returns contained
in the original source file. Hence, no lines ever get moved to the
left as a result of formatting and any special formatting the user
has done remains unchanged as long as it places text farther to the
right than PRETTY requires.
The user may request, as an option, that all leading blanks be
removed except before comments (PRETTY prompts for this option). This
has the effect of placing all non-comment text as far left as the
formatting conventions allow.
The user may also request that PRETTY capitalize all Pascal
reserved words.
FORMATTING CONVENTIONS
The current formatting conventions are as follows (taken from
the source of PRETTY).
[ General PrettyPrinting Rules ]
1. Any spaces or blank lines beyond those generated by the
PrettyPrinter are left alone. The user is encouraged, for the
sake of readability, to make use of this facility.
In addition, comments are left where they are found, unless
they are shifted right by preceding text on a line.
2. All declarations and all "FOR", "WHILE", "WITH", and "LOOP"
statements begin on separate lines.
3. No line may be greater than 128 characters long. Any line
longer than this is continued on a separate line.
4. The keywords "BEGIN", "END", "REPEAT", and "RECORD" are
forced to stand on lines by themselves (or possibly follwed by
supporting comments).
In addition, the "UNTIL" clause of a "REPEAT-UNTIL" state-
ment is forced to start on a new line.
5. A blank line is forced before the keywords "PROGRAM",
"PROCEDURE", "FUNCTION", "LABEL", "CONST", "TYPE", and "VAR".
6. A space is forced before and after the symbols ":=" and
"=" additionally, a space is forced after the symbol ":".
[ indentation rules ]
1. The bodies of "LABEL", "CONST", "TYPE", and "VAR" declara-
tions are indented from their corresponding declaration header
keywords.
2. The bodies of "BEGIN-END", "REPEAT-UNTIL", "FOR", "WHILE",
"WITH", and "CASE" statements, as well as "RECORD-END" struc-
tures and "CASE" variants (to one level) are indented from
their header keywords.
3. An "IF-THEN-ELSE" statement is indented as follows:
IF <expression>
THEN
<statement>
ELSE
<statement>
however, none of the line breaks illustrated is required.
4. A sequence of "IF-THEN-ELSE IF-THEN-ELSE IF..." is indented
IF <expression>
THEN
<statement>
ELSE IF <expression>
THEN
. . .
ELSE
<statement>
each "ELSE IF" appears on a new line. The "ELSE" and the "IF"
should appear on the same line in the input source text.
5. A sequence of "IF-THEN " is indented
IF <expression>
THEN IF <expression> ...
THEN
<statement> ....
each "THEN IF" appears on a new line. The "THEN" and the "IF"
should appear on the same line in the source text.
RUNNING PRETTY
To use PRETTY, run it from monitor level with the command
@<PH0Q>PRETTY
The program will prompt for input and output files. File name
recognition will not work at this point. If you choose the name of the
output file to be the same as that of the input file, you will be asked
to confirm that you want the output file deleted.
ACKNOWLEDGEMENTS
PRETTY was written by H. Ledgard and J. Hueras of the University
of Massachusetts. P. N. Hilfinger of CMU modified it to run on the
TOPS-10 and TOPS-20 operating systems and the CMU version of Pascal.
The latter also made some modifications in the formatting conventions.
Additional modifications by Michael E. Fryd.
PRETTY is currently unsupported. Send suggestions to <PH0Q>.