# *********************************************************************
# compute.txt: help text
# Copyright (c) 2001,2006 Carlo Strozzi
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 dated June, 1991.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
# *********************************************************************
# $Id: compute.txt,v 1.4 2006/03/10 11:26:13 carlo Exp $

                      NoSQL operator: compute

Applies arbitrary AWK expressions to table data, using column names.

Usage: compute [options] expression

Options:
    --input (-i) 'file'
      Read input from 'file' instead of STDIN.

    --output (-o) 'file'
      Write output to 'file' instead of STDOUT.

    --help (-h)
      Display this help text.

    --no-header (-N)
      Remove header from output.

    --debug (-x)
      Display the resulting awk(1) program before running it.

Notes:

If the input table contains duplicated columns, i.e. columns with the        
same name but possibly different values, only the first (leftmost) one       
is taken into account. The output will still have the duplicates, but
this time with equal column values.

If no expression is specified, then the program exits with an error
message.

The following names are reserved to the awk language, and should not
be used to indicate column names:

BEGIN, END, break, continue, else, exit, exp, for, getline, if, in,
index, int, length, log, next, print, printf, split, sprintf, sqrt,
substr, while, and possibly others. See mawk(1) for more on this.
Furthermore, the '_nosql_' prefix is reserved for internal NoSQL use,
and should never be used at the beginning of column names.

This NoSQL operator reads a table from STDIN and writes a
table to STDOUT.

