link printcol
August 14, 1996; Robert J. Alexander
This file is in the public domain.
This procedure deals with with the problem of printing tabular
data where the total width of items to be printed is wider than
the page. Simply allowing the data to wrap to additional lines
often produces marginally readable output. This procedure facil-
itates printing such groups of data as vertical columns down the
page length, instead of as horizontal rows across the page. That
way many, many fields can be printed neatly. The programming of
such a transformation can be a nuisance. This procedure does
much of the work for you, like deciding how many items can fit
across the page width and ensuring that entire items will be
printed on the same page without page breaks (if that service is
requested).
____________________________________________________________
For example, suppose we have a list of records we would like
to print. The record is defined as:
record rec(item1,item2,item3,...)
Also suppose that lines such as
Field 1 Field 2 Field 3 ...
------- ------- ------- ---
Record 1 item1 item2 item3 ...
Record 2 item1 item2 item3 ...
are too long to print across the page. This procedure will print
them as:
TITLE
=====
Record 1 Record 2 ...
-------- -------- ---
Field 1 item1 item1 ...
Field 2 item2 item2 ...
Field 3 item3 item3 ...
The arguments are:
items: a co-expression that produces a sequence of
items (usually structured data objects, but not
necessarily) for which data is to be printed.
fields: a list of procedures to produce the field's
data. Each procedure takes two arguments. The
procedure's action depends upon what is passed
in the first argument:
header Produces the row heading string to be used
for that field (the field name).
width Produces the maximum field width that can
be produced (including the column header).
Other Produces the field value string for the
item passed as the argument.
The second argument is arbitrary data from the procedures
with each invocation. The data returned by the first func-
tion on the list is used as a column heading string (the
item name).
title: optional.
pagelength: if null (omitted) page breaks are ignored.
linelength: default 80.
auxdata: auxiliary arbitrary data to be passed to the field
procedures -- see `fields', above.