⟦53684c91a⟧

TextFile

% This is PROGDOC.DOC                     as of 05 Dec 88
%---------------------------------------------------------
% (c) 1988 by J.Schrod. Put into the public domain.

%
% Macro package for the documentation of programs (and TeX macros)
% english version
%

%
% first version (for ftp/Bitnet)                                   (88-12-05)
%



% documented with itself...
\input progdoc


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% local macros
%

\font\mc=cmr9           % for names like ASCII
\font\sc=cmcsc10        % caps and small caps 10pt

\def\WEB{{\tt WEB\/}}
\def\LaTeX{{\rm L\kern-.36em\raise.3ex\hbox{\sc a}\kern-.15em\TeX}}

%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%





\chap Introduction.

\WEB{} systems allow the documentation of programs by supporting the
separation in program fragments which can be collected and rearranged
afterwards.  This allows {\it top-down\/} programming as well as the
{\it bottom-up\/} design of programs.  Each program fragment can be
documented, usually with \TeX{}.  A disadvantadge is that \WEB{}
actually exists only for a few programming languages (Pascal, C,
Modula-2).  Besides, building up \WEB{} systems for ``exotic''
programming languages like \TeX{} is very difficult.

This macro package was built to allow good documentation for programs
in languages for which \WEB{} doesn't exist.  It separates a program
text in sections that can be documented.  All sections, collected
sequentially, will result in the complete program.  In every section
begin and end of the program part are marked with |\beginprog| and
|\endprog|, this program part will be formatted as it is input
(``verbatim'').

The separation of the sections is done in this version (which is based
on Plain~\TeX{}) by the macros |\chap| and |\sect|.  But this can be
changed easily, e.g.\ for preparing the documentation with \LaTeX{}.
Then the last section group of this macro package must be omitted and
the rest must be realized as a style option.

In the documentation part of a section text pieces, e.g.\ names of
variables, can be inserted verbatim to demonstrate the connection to
the program text.  These parts are included in vertical bars
(`{\tt\vbar}') while the vertical bar itself can be obtained by
|\origvert|.

This macro package does not offer the creation of an index because it
is not known which syntactical tokens the language has that should be
mentioned in an index.  As well the creation of a table of contents
and of headings would be preferable to allow better orientation in the
document.  Some remarks about future enhancements which should be done
urgently are set in slanted type.


\sect We have to realize three parts:  (1)~the formatting of rather
small verbatim texts in a line, (2)~the formatting of larger parts of
program and (3)~the document structuring elements for the separation
of the sections.  Before we start we declare some shorthands for
category codes.

By declaring the at sign~(`|@|') as well as the underscore~`(|_|)' as
letters we can use them in our macros.
{\tolerance=10000
(I agree with D.~Knuth that |\identifier_several_words_long| is much
better readable than |\IdentifierSeveralWordsLong| and both are better
than |\pr@@@s|.)
With the at sign we can use the ``private'' Plain macros and with the
underscore we can make our own macros more readable.  But as we have
to restore these category codes at the end of this macro file we store
their former values in the control sequences |\atcode| and |\uscode|.
This method is better than the usage of a group because not all macros
have to be defined global this way.
\par}

\beginprog
\chardef\escape=0
\chardef\letter=11
\chardef\other=12
%\chardef\active=13              % is defined in Plain already

\chardef\atcode=\catcode`\@
\chardef\uscode=\catcode`\_

\catcode`\@=\letter
\catcode`\_=\letter
\endprog




\chap Local Verbatim Formatting.

The main point of every verbatim formatting is the switching of the
character codes of all characters that have a special \TeX{} meaning.
This can be done with the control sequence |\dospecials| that applies
the control sequence |\do| to all special characters.  Additionally,
every line is regarded as a paragraph without indentation.  Between
two paragraphs, i.e.\ between two lines, no extra space is set.
Finally all blanks and tabular characters shall be obeyed and the
inter word space after sentence terminators shall not be enlarged.
The activation of the tabular characters with |\obeytabs| is
equivalent to |\obeyspaces| in {\tt plain.tex\/}.

Verbatim texts are set in monospace, we use (like in \WEB{}) the
character set with the extended {\mc ASCII}.  For \LaTeX{} we would
have to add here |\ttex| to all size modifications like |\xpt|,
|\xiipt|, etc.

\beginprog
\font\tentex=cmtex10            % typewriter extended ASCII 10pt
\let\ttex=\tentex               % only for PLAIN with base size 10pt

\def\setup_verbatim{%
   \def\do##1{\catcode`##1\other}\dospecials
   \parskip\z@skip \parindent\z@
   \obeylines \obeyspaces \obeytabs \frenchspacing
   \ttex
   }

\let\tab=\space
\begingroup
   \catcode`\^^I=\active%       % Attention: no tabs!
   \gdef\obeytabs{\catcode`\^^I=\active\def^^I{\tab}}
   \global\let^^I=\tab%         % if an active tab appears in a \write
\endgroup
\endprog

\sect After having saved the old meaning of `{\tt\vbar}' in
|\origvert| and after declaring |\vbar| as a synonym for the character
that has the code of a vertical bar in the actual font, the vertical
bar can be made active.  Then we call |\setup_verbatim|.  But the
newline characters shall not be processed, they shall be regarded like
blank space.  This can be reached by defining |\par| as |\space|.

The next vertical bar in the input closes the group which becomes an
(unbreakable) |\hbox| then.  The old meanings of the special
characters and of the vertical bar are restored and \TeX{} is in
normal (horizontal) mode again.

\beginprog
\let\origvert=|
\chardef\vbar=`\|

\catcode`\|=\active

\def|{%
   \leavevmode
   \hbox\bgroup
      \let\par\space \setup_verbatim
      \let|\egroup
   }
\endprog




\chap  Program Fragments in Verbatim.

We need macros to format the program fragments without any
linebreaking.  Such a text area shall start with the macro
|\beginprog| and end with |\endprog|.  The macro |\endprog| must stand
at the very beginning of a line and must be followed by white space
(blank, tab or newline character).  After |\beginprog| as well as
after |\endprog| the rest of the line is ignored.

Two demands must be regarded:  There should be no length restrictions
for the processed text, and the tabular characters should be expanded
so that this macro works on PC's and on VAXes, too.


\sect The implementation method is quite simple:  We read the next
line, test, wether the end is reached (by comparing with |\endprog|)
and otherwise set the character actually read.  Every character is
inspected and tabular characters are expanded.

Wether a line is set or wether the end of the processed area is
reached is indicated by the switch |\if@print|.  At the beginning of
the |\beginprog| macro most settings are done with |\setup_verbatim|
(the vertical bar must be handled separately) and the rest of the line
is ignored.  As everything is done within a group, the end of the
verbatim text can be processed by simply closing this group.

For the user it looks as if |\endprog| terminates the processing, but
it just serves for the identification of the end, the true processing
is done with the internal macro |\end_verbatim|.

\beginprog
\newif\if@print

\def\beginprog{%
   \endgraf
   \bigbreak
   \begingroup
      \setup_verbatim \catcode`\|\other
      \@printtrue
      \ignore_rest_line
   }
\let\end_verbatim=\endgroup             % internal command !
\endprog


\sect The first line is ignored, all the other lines are identified
with |\set_next_line| and processed with |\do_set|.  This separation
in identification and processing allows that the line end character is
active in the definition only for a short time.

When a line is to be formatted, we first check with |\check_print|
wether it contains |\endprog|, otherwise it is printed with
|\print_char|.  The printing must be done for every character
individually because we want to check for tabular characters; the
exact algorithm is described below.  Here we just have to note that
|\print_char| is used with two parameters of which the second one is
finished with the token |\end_line|.  The first parameter is the first
character of the line, the second parameter is the rest of the line.
If the line is empty, the argument of |\do_set| is empty, too; so the
activation of |\print_char| must be finished with two |\end_line|.
Then the first |\end_line| is the first argument for |\print_char| and
the second argument is empty.  But if the line did contain something,
the second |\end_line| is evaluated, for this case it is defined as
|\relax|.

At last we call |\set_next_line| again to format the next line.  If
the end is reached, i.e.\ if a line with |\endprog| was found,
|\set_next_line| is redefined as |\relax|.  This can be done because
the original meaning is restored while closing the group with
|\end_verbatim|.

\beginprog
\begingroup
   \obeylines%          % ^^M is active! ==> every line must end with %
   \gdef\ignore_rest_line#1^^M{\set_next_line}%
   \gdef\set_next_line#1^^M{\do_set{#1}}%
\endgroup

\def\do_set#1{%
   \endgraf
   \check_print{#1}%
   \if@print  \indent \print_char#1\end_line\end_line
   \else  \let\set_next_line\end_verbatim
   \fi
   \set_next_line
   }
\let\end_line=\relax
\endprog


\sect Before we look at the problem of formatting a line, we declare
|\check_print| that checks the end of the verbatim mode.  We have to
do two things:  we must split everything in front of the first blank
or tabular character and compare for identity with |\endprog|.  The
splitting is easy because the line which is our first argument
contains blanks and tabulators as active characters.  First we call
|\cut_at_tab| that demands a tabular character as separator for its
two pramenters so that everything in the line in front of the first
tabulator is part of the first parameter.  If there is no tabular
character in the line, we append one so that the second parameter is
empty.  The same trick is used to separate the part in front of the
first blank character from the resulting first part.

The check is done with |\do_check|.  We use a separate macro here so
that we can indent it (in the following definition blanks are active!)

\beginprog
\begingroup
\obeyspaces\obeytabs
\gdef\check_print#1{\cut_at_tab#1^^I\end_line}
\gdef\cut_at_tab#1^^I#2\end_line{\check_first_part#1 \end_line}% blank !
\gdef\check_first_part#1 #2\end_line{\do_check{#1}}
\endgroup
\endprog


\sect |\do_check| compares the line with a sample line that is
available in |\@endverbatim|.  During the definition of
|\@endverbatim| it must be cared for that the escape character `|\|'
is a printable character:  A comparison with |\ifx| demands identical
category codes.  As a temporary escape character we use the vertical
bar.

\beginprog
\def\do_check#1{%
   \def\@line{#1}%
   \ifx \@line\@endverbatim  \@printfalse
   \fi
   }

{\catcode`\|=\escape  \catcode`\\=\other % | is temporary escape char
   |gdef|@endverbatim{\endprog}          % sample line
}                                        % here \endgroup can't be used
\endprog


\sect Now we can set a line:  we start with the first character,
followed by the rest of the line.  Each character is counted in
|\char_count|.  At the beginning of a line |\char_count| is~1, this
is reset at the end of the line.

\goodbreak

\beginprog
\newcount\char_count  \char_count\@ne

\def\print_char#1#2\end_line{%
   \print_first_char{#1}%
   \print_rest_of_line{#2}%
   }
\endprog


\sect For each character that is set |\char_count| is incremented.
If a character is a tabulator, we set with |\print_tab| the fitting
amount of blank characters, otherwise the character itself.  We must
compare the character that is stored in |\@char| with a macro of which
the ``first-level'' expansion is an active tabulator.  For this case
we declare |\@tab|.

\beginprog
{\obeytabs\gdef\@tab{^^I}}

\def\print_first_char#1{%
   \def\@char{#1}%
   \advance \char_count\@ne
   \ifx \@char\@tab  \print_tab
   \else  \@char
   \fi
   }
\endprog


\sect If we want to fill the line with blank spaces up to the next
column with a number that can be divided by~8, we must be able to
compute the column number modulo~8, but \TeX{} has no modulo operator.
So we define the macro |\mod_viii| that computes its argument modulo~8
and returns the result in the counter |\count_mod_viii|.  For the
computation we need the temporary counter |\count@|.

\beginprog
\newcount\count_mod_viii
\def\mod_viii#1{%
   \count@ #1\relax  \count_mod_viii\count@
   \divide \count@ 8\relax
   \multiply \count@ 8\relax
   \advance \count_mod_viii -\count@
   }
\endprog


\sect Now we can declare |\print_tab|.  We must remember that
|\char_count| was incremented already, if we set only one blank
character the counter keeps untouched.

\beginprog
\def\print_tab{%
   \loop  \space \mod_viii\char_count
      \ifnum \count_mod_viii>\z@
         \advance \char_count\@ne
   \repeat
   }
\endprog


\sect If the rest of the line is empty, we are ready.  |\char_count|
is reset to~1 for the next line.

Inside the |\else| part of |\ifx| |\print_char| should not be used
directly because this costs too much storage of \TeX{}.  Instead we
set a control sequence |\next| that is processed afterwards, depending
on the result of the comparison.  If there is still something to set,
we use |\print_char| again, otherwise a syntactically similar macro
that expands to |\relax|.

\beginprog
\def\print_rest_of_line#1{%
   \def\@line{#1}%
   \ifx \@line\empty  \char_count\@ne
        \def\next##1\end_line{\relax}%
   \else  \let\next\print_char
   \fi
   \next#1\end_line
   }
\endprog




\chap Document Structuring.

The layout of the document shall be like in \WEB{}.  This can be done
easily in Plain.  If \LaTeX{} shall be used for the document
preparation, this part of the macro must be eliminated.  It will also
be better to include the program parts \LaTeX-like as an environment
between |\begin{prog}| and |\end{prog}| and to define control
sequences |\makebaractive| and |\makebarother| for the switch of the
special meaning of the vertical bar (`{\tt \origvert\/}') (for the
{\tt tabular\/} environment!)

All sections are enumerated, the number of the next section is stored
in the counter |\sectno|.  We differenciate between main sections
which start a group of sections and between normal sections within a
group.

\beginprog
\newcount\sectno  \sectno=\@ne
\endprog


\sect The main sections are started with the macro |\chap| that has
one parameter, the title of the section group.  This parameter must be
terminated by a dot.  We start a new page, typeset the title in bold
face and separate it from the section text with a |\medskip|.  This
text, the documentation part of the section, is formatted without
paragraph indentation.

The deletion of the paragraph indentation is done with |\everypar|.
We do not care if |\everypar| is used for something else and delete it
after usage.

\begingroup \sl
Here the title, the section and the page number should be written to
an auxiliary file so that a table of contents could be created at the
end of the run (at |\bye|), and the dealing with |\everypar| should
not be so cruel.
\endgroup

\beginprog
\def\chap#1.{%
   \endgraf
   \vfill\eject
   \noindent {\bf \number\sectno.\quad #1.}%
   \advance \sectno\@ne
   \endgraf
   \medskip  \nobreak
   \everypar{%
      \setbox0\lastbox
      \global\everypar{}%
      }%
   }
\endprog


\sect Normal sections are started with |\sect|.  This macro has no
parameter.  Between two paragraphs we set 2~pica space (if possible)
and prefer the page breaking.  Between the section number and the text
one quad of space is set.

\begingroup \sl
The page break manipulation could be more sophisticated.
\endgroup

\beginprog
\def\sect{%
   \endgraf
   \vskip 2pc plus 1pc minus 6dd  \goodbreak
   \noindent {\bf \number\sectno.}\advance \sectno\@ne
   \quad \ignorespaces
   }
\endprog


\sect We are finished and just have to restore the category codes.

\beginprog
\catcode`\@=\atcode
\catcode`\_=\uscode

\endinput
\endprog





\bye
DataMuseum.dk

DKUUG/EUUG Conference tapes

⟦53684c91a⟧ TextFile

Derivation

TextFile
