XTRAN Example — Format Text Items into Columns

Scenario — you have a list of text items, and you want to format them into descending columns.  It is an onerous editing task, even using edit macros.

XTRAN to the rescue!

The following example uses an XTRAN rules file comprising 120 non-comment lines of "meta-code" (XTRAN's rules language) to format text items into columns.

The rules took less than 1½ hours to write and 1 hour to debug.  (That's right, less than 2½ hours total!)

The rules read a series of text items from a file, one per line, format them into columns, and write out the result. They allow you to specify, via environment variables:

• Whether to create the output file or append to it.
• The number of columns you want.
• Whether each item in a column is to be left-justified, right-justified, or centered.
• The number of spaces between columns (column padding).

How can such powerful and generalized text manipulation be automated in less than 2½ hours and only 120 lines of rules?  Because there is so much capability already available as part of XTRAN's rules language.  These rules take advantage of the following functionality:

• Text file input and output
• Text manipulation
• Text formatting
• Delimited list manipulation
• Environment variable manipulation
• Content-addressable data bases

The input to and output from XTRAN are untouched.

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Process Flowchart

Here is a flowchart for this process, in which the elements are color coded:

• BLUE for XTRAN versions (runnable programs)
• ORANGE for XTRAN rules (text files)
• PURPLE for text data files

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Input to XTRAN:

When
in
the
course
of
human
events
it
becomes
necessary
for
one
nation
to
dissolve
the
political
bonds
which
have
connected
it
with
another

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Output from XTRAN — left justified:

When      events       nation       which
in        it           to           have    
the       becomes      dissolve     connected
course    necessary    the          it
of        for          political    with
human     one          bonds        another

Output from XTRAN — right justified:

  When       events       nation        which
    in           it           to         have
   the      becomes     dissolve    connected
course    necessary          the           it
    of          for    political         with
 human          one        bonds      another

Output from XTRAN — centered:

 When      events       nation        which
  in         it           to          have  
 the       becomes     dissolve     connected
course    necessary       the          it
  of         for       political      with
human        one         bonds       another