Designing a Business Card in LaTeX(olivierpieters.be)

     \newread\XREFileIn
      % \message{\string\XREFileIn = \the\XREFileIn}
      \newwrite\XREFileOut
      %
      \newcount\SNChapter
      \newcount\SNUnit
      \newcount\SNTable
      \newcount\SNFigure
      %
      \SNChapter=0
      \SNTable=0
      \SNFigure=0
      %
      \def\SNChapterPrefix{}
      %
      \def\TrimTag#1 {#1}          % For trimming trailing blanks.
      \def\First#1 #2 #3 {#1}      % Parsing first token.
      \def\Second#1 #2 #3 {#2}     %   "     second "
      \def\Third#1 #2 #3 {#3}      %   "     third  "
      \def\SNUNone{CH UN PG}       % Value for tags before there is an XRF file.
      \def\SNTNone{TB JUNK PG}     % Value for tags before there is an XRF file.
      \def\SNFNone{FG JUNK PG}     % Value for tags before there is an XRF file.
      \def\SNPNone{PT JUNK PG}     % Value for tags before there is an XRF file.
      %
      \def\SNUAdvanceChapter{\advance\SNChapter by1
      \SNUnit=0}
      %
      % Define a 'chapter' tag:
      %
      % Need a \global on \advance because might have the \SNC from
      % within a group, e.g., {\bf \SNC ...}.
      %
      \def\SNC#1{{\global\SNUnit=0
      \write\XREFileOut{\string#1}%
      \def\JUNKA{\SNChapterPrefix\the\SNChapter\space JUNK}%
      {\edef\JUNKB{\write\XREFileOut{\JUNKA}}\JUNKB}%
      \write\XREFileOut{\the\count0}}}%
      %
      % Define a 'unit' tag:
      %
      % To be more sure page number is correct, add text to list
      % BEFORE writing page number to XRF file.  In principle could
      % do the same for \SNT and \SNF but from how these are used in
      % practice a page number error would be nearly impossible.
      %
      \def\SNU#1{{\global\advance\SNUnit by1
      \write\XREFileOut{\string#1}%
      \SNChapterPrefix\the\SNChapter.\the\SNUnit
      \def\JUNKA{\SNChapterPrefix\the\SNChapter\space\the\SNUnit}%
      {\edef\JUNKB{\write\XREFileOut{\JUNKA}}\JUNKB}%
      \write\XREFileOut{\the\count0}}}%
      %
      % BEGIN Modified at 04:16:31 on Tuesday, December 29th, 2015.
      %
      %    In this collection, we now have a new
      %    macro
      %
      %         \SNP -- Sequentially Number Pointer
      %
      %    This macro intended for cross
      %    referencing to a place in text, that
      %    is not specifically to a 'unit'
      %    (definition, theorem), table, or
      %    figure.
      %
      %    In short, can have
      %
      %         Note\SNP{\SNTagCU}
      %         that, for $a, b \in R$ and
      %
      %    which will define tag \SNTagCU but
      %    insert nothing into the document.
      %
      %    Then elsewhere can have
      %
      %         Since as on page
      %         \SNCGetPage{\SNTagCU}
      %         an inner product is bilinear,
      %
      %    which will insert into the document
      %    the page number of the page where the
      %    macro \SNTagCU was defined.  Many
      %    more details below:
      %
      %    The macro \SNP is part of this
      %    package of cross referencing and
      %    sequential numbering but does not
      %    actually 'number' or 'sequentially
      %    number' anything.  We start the name
      %    of \SNP with 'SN' just to regard
      %    macro names of the form SNx as
      %    'reserved' in own TeX usage.
      %
      %    Then elsewhere in the document, can
      %    refer to that place by its page
      %    number, chapter number (apparently
      %    with its chapter prefix), etc.
      %
      %    E.g., if give a little discussion of,
      %    say, bilinear, can type, say,
      %
      %         Note\SNP{\SNTagCU}
      %         that, for $a, b \in R$ and
      %
      %    and that will just 'define' tag
      %    SNTagCU.  Of course the tag SNTagCU
      %    was likely from running own KEdit
      %    macro isntag to find the new tag name
      %    SNTagCU and insert it in the argument
      %    of the macro \SPP. That is, in KEdit
      %    we would have line
      %
      %         Note\SNP{}
      %
      %    current, run KEdit macro isntag, and
      %    get a new tag found an inserted to
      %    have something like
      %
      %         Note\SNP{\SNTagCU}
      %
      %    Then elsewhere in the document can
      %    write, say,
      %
      %         Since as on page
      %         \SNCGetPage{\SNTagCU}
      %         an inner product is bilinear,
      %
      %    and get the page number of the page
      %    in the document with
      %
      %         Note\SNP{\SNTagCU}
      %
      %    that is, where tag \SNTagCU was
      %    defined.
      %
      %    So, the lines
      %
      %         Note\SNP{\SNTagCU}
      %         that, for $a, b \in R$ and
      %
      %    write to the XRF file the standard
      %    three lines that would be written by,
      %    say, macro \SNU. With those three
      %    lines, the first has the tag
      %
      %         \SNTagCU
      %
      %    the next line has chapter and unit
      %    and the third line has the page
      %    number, all for what was the case for
      %    that part of that page when the macro
      %    \SNP was run.
      %
      %    Then, macros
      %
      %         \SNUGetChapter\SNTagCU
      %         \SNUGetUnit\SNTagCU
      %         \SNUGetPage\SNTagCU
      %
      %    will all work fine to extract the
      %    data on, respectively, chapter, unit,
      %    and page and insert it into the
      %    document.  That is, there is no
      %    reason to have separate macros to
      %    extract and for macro \SNP.
      %
      %    Really the macro \SNP is just like
      %    macro \SNU except does not add 1 to
      %    SNUnit and does not insert into the
      %    document the chapter prefix, chapter
      %    number, and unit number.  So, where
      %    macro \SNP is used, nothing is
      %    inserted into the document; this is
      %    in contrast with, say, macro \SNU and
      %    is why need the new macro \SNT
      %

      % XREF001.TEX --
      %
      % Created at 02:29:35 on Thursday, April 13th, 2006.
      % ======================================================================
      %
      % Modified at 01:03:52 on Thursday, April 13th, 2006.
      %
      %    Macros for sequential numbering and cross-references
      %
      %    Macros \SNUAdvanceChapter, \SNU#1, \SNT#1, \SNF#1,
      %         \GetSN, \SNC#1, \SNCGetChapter#1, \SNCGetPage#1,
      %         \SNUGetChapter#1, \SNUGetUnit#1, \SNUGetPage#1,
      %         \SNTGetTable#1, \SNTGetPage#1, \SNFGetFigure#1,
      %         \SNFGetPage#1, \SNChapterPrefix
      %
      %    Counters \SNChapter, \SNUnit, \SNTable, \SNFigure,
      %
      %    Here SN abbreviates 'sequential numbering'.
      %
      %    Here we have a start on a fairly general collection of
      %    macros for sequential numbering and cross-referencing.
      %
      %    For example, maybe in some chapter, that at present is
      %    chapter 3, we want to sequentially number definitions,
      %    theorems, remarks, and examples -- call them all 'units'
      %    -- as in:
      %
      %         3.1 Definition:
      %
      %         3.2 Theorem:
      %
      %         3.3 Definition:
      %
      %         3.4 Remark:
      %
      %         3.5 Example:
      %
      %    Then with this package we would select some tags, say,
      %    starting with SNTag, and type
      %
      %         \SNU{\SNTagA} Definition:
      %
      %         \SNU{\SNTagB} Theorem:
      %
      %         \SNU{\SNTagC} Definition:
      %
      %         \SNU{\SNTagD} Remark:
      %
      %         \SNU{\SNTagE} Example:
      %
      %    So, macro \SNU abbreviates 'sequential numbering with
      %    units'.  So, with macro \SNU we get a case of automatic
      %    sequential numbering.
      %
      %    Suppose 3.1 Definition: appeared on page 43.  Then
      %    elsewhere we could write
      %
      %         See \SNUGetChapter\SNTagA.\SNUGetUnit\SNTagA Theorem
      %         on page \SNUGetPage\SNTagA.
      %
      %    and get
      %
      %         See 3.1 Theorem on page 43.
      %
      %    So, we get automatic cross-referencing.
      %
      %    Of course, to do cross-referencing in such a general way,
      %    need to run TeX at least twice, once to find, for each
      %    sequentially numbered 'unit', its page and write this
      %    data to a file, and once to read this file and insert the
      %    sequential numbering and page numbers where desired in
      %    cross-references.
      %
      %    The file is \jobname.XRF.
      %
      %    To use this sequential numbering with units,
      %
      %         o    At each chapter, after the \eject, if there is
      %              one, and just before the \hOne, have
      %
      %                   \SNUAdvanceChapter
      %
      %              to increment by one the counter \SNChapter and
      %              set the counter \SNUnit to 0.
      %
      %         o    Otherwise use macros
      %
      %                   \SNU\SNTagA
      %                   \SNUGetChapter\SNTagA
      %                   \SNUGetUnit\SNTagA
      %                   \SNUGetPage\SNTagA
      %
      %              as illustrated.
      %
      %         o    Then run TeX at least twice, basically until
      %              the file \jobname.XRF quits changing.
      %
      %    So, we get sequential numbering and cross-referencing with
      %    'units'.  The macros and counters particular to 'units'
      %    all begin with \SNU.
      %
      %    We let
      %
      %         \newcount\SNUnit
      %
      %    keep track of the number of the unit.  So, when we use
      %
      %         \def\SNUAdvanceChapter{\advance\SNChapter by1
      %         \SNUnit=0}
      %
      %    to increment
      %
      %         \newcount\SNChapter
      %
      %    we also set \SNUnit=0 for the new chapter.
      %
      %    With the \SNU macros as illustrated, will get file
      %    \jobnane.XRF like
      %
      %         \SNTagA
      %         1 1
      %         1
      %         \SNTagB
      %         1 2
      %         1
      %         \SNTagC
      %         1 3
      %         1
      %         \SNTagD
      %         1 4
      %         1
      %         \SNTagE
      %         1 5
      %         1
      %         \SNTagF
      %         1 6
      %         1
      %         \SNTagG
      %         1 7
      %         1
      %         \SNTagH
      %         1 8
      %         1
      %         \SNTagI
      %         1 9
      %         1
      %
      %    So, get three lines for each invocation of \SNU.  The
      %    first line has the tag.  The second line has data
      %    particular to 'units' macros.  And the third line has the
      %    page number.
      %
      %    For in Appendix I, may want units to go
      %
      %         A.I.1.2
      %
      %    that is, to have a 'prefix' of 'A.I.'.  To this end there
      %    is macro
      %
      %         SNChapterPrefix
      %
      %    which is default empty.  Setting this macro to
      %
      %         \def\SNChapterPrefix{A.I.}
      %
      %    will give the prefix 'A.I.'.  But, such a prefix should
      %    have no blanks else the parsing of the macros that get
      %    cross-referencing information will get confused!
      %
      %    But we may also want sequential numbering and
      %    cross-referencing for tables, figures, equations, etc.
      %
      %    Then the idea is to have more sequential numbering
      %    macros.  But, do not want a proliferation of files.  So,
      %    these other macros should also use the file \jobname.XRF.
      %    For compatibility, each of these other macros should also
      %    write three lines to file \jobname.XRF.  The main freedom
      %    is just in the second line.
      %
      %    Each tag, e.g., \SNTagA, becomes a macro.  So, each tag
      %    should be spelled like a TeX macro and have spelling
      %    different from all other TeX macros in use.
      %
      %    During the first pass of TeX, macros
      %
      %         \SNUGetChapter\SNTagA
      %
      %         \SNUGetUnit\SNTagA
      %
      %         \SNUGetPage\SNTagA
      %
      %    will notice that \SNTagA is not defined and will define
      %    it as the macro \SNUNone from
      %
      %         \def\SNUNone{CH UN PG}
      %
      %    the three tokens of which are intended to abbreviate,
      %    respectively, chapter, unit, and page.
      %
      %    Then each of the three macros
      %
      %         \SNUGetChapter\SNTagA
      %
      %         \SNUGetUnit\SNTagA
      %
      %         \SNUGetPage\SNTagA
      %
      %    will return 'CH', 'UN', and 'PG', respectively, as
      %    temporary place holders and a way to get page breaking
      %    approximately correct before another pass of TeX that
      %    will read and use the XRF file written on the previous
      %    pass.
      %
      %    We also have macros for tables and figures.  For tables,
      %    the names begin with SNT; figures, SNF.
      %
      %    The main challenge was in macro SNU (SNT, SNF) that has
      %    to write both the sequential numbering and the page
      %    number.  The cause of the challenge was how, really,
      %    when, TeX actually does page breaking.  So, once TeX
      %    starts a new page, it keeps adding lines until it clearly
      %    has enough, and maybe too many, lines for that page.
      %    Then TeX decides where to break the page, uses any left
      %    over lines for the next page, and continues.  So, when a
      %    macro in the text executes, TeX does not yet know the
      %    page number but the macro does know the chapter number
      %    and, say, the unit number.
      %
      %    When TeX sees a \write, TeX temporarily puts the \write
      %    in a 'whatsit' until the page breaking and then executes
      %    the \write.  'Whatsits' are discussed starting a line
      %    14,007 of the file of TEXBOOK.TEX.
      %
      %    The trick, then, is to have
      %
      %         \def\JUNKA{\the\SNChapter\space\the\SNUnit}
      %         {\edef\JUNKB{\write\XREFileOut{\JUNKA}}\JUNKB}
      %         \write\XREFileOut{\the\count0}
      %
      %    In the first line we define \JUNKA that has the data to
      %    be written.  The second line has a group with an \edef
      %    (define a macro expanded immediately) of a temporary
      %    macro \JUNKB with the \write and with the data to be
      %    written and, then, with an invocation of \JUNKB.  Due to
      %    the \edef, the whatsit for the \write has only constants
      %    and the right constants.  Those constants are from
      %    counters
      %
      %         \SNChapter
      %         \SNUnit
      %
      %    which might well change by the time the \write is
      %    executed; but, the constants will still have the values
      %    we need to have written.
      %
      %    On the third line, we use \write to write the page
      %    number, and the page number in \count0 is expanded at the
      %    time of the page breaking and, thus, has the correct page
      %    number.
      %
      %    Another challenge is how to handle the data read from
      %    file \jobname.XRF:  As each line is read, it has a
      %    trailing blank.  So, have to use and/or parse the blank.
      %