= define-structure =

This is a Chicken Scheme egg which implements a QobiScheme-compatible
''define-structure'' macro. The resulting object is implemented as a
chicken record. It automatically sets up reader syntax for reading and
writing the object. It also integrates with the nondeterminism egg,
see ''local-set-{name}-{field}!''.

==== Creation ====

:(define-structure name . fields)

Creates a new structure.

==== Use ====

The following functions are generated when creating a structure. 

:(make-{name} {field0-value} {field1-value} ...)
:(make-keywords-{name} {field-name}: {field-value} ...)

Any fields not defined in ''make-keywords-{name}'' will be uninitialized.

:({name}? obj)

Tests if ''obj'' is of a ''{name}'' record.

:({name}-{field} obj)

Accesses the field.

:({name}-{field}-set! obj val)
:(set-{name}-{field}! obj val)

The former is created by chicken's ''define-record'', the latter is
added for compatbility with QobiScheme. 

:({name}-{field}-setp! obj proc)
:(setp-{name}-{field}! obj proc)

Like ''set-'' but calls ''proc'' witht he current value and updates it
to what ''proc'' returns.

:(local-set-{name}-{field}! obj val)
:(local-setp-{name}-{field}! obj proc)

This set! will be undone when backtracking with the nondeterminism
egg.

:({name}-{field}-update obj val)
:(update-{name}-{field} obj val)
:({name}-{field}-updatep obj proc)
:(updatep-{name}-{field} obj proc)

like the ''set'' and ''setp'' versions but these return a new copy of
the object.

:(set-{name}! obj {field-key}: {field-value} ...)
:(setp-{name}! obj {field-key}: {field-value} ...)
:(update-{name} obj {field-key}: {field-value} ...)
:(updatep-{name} obj {field-key}: {field-value} ...)

As above but with keywords.

:(alist->{name} alist)
:({name}->alist obj)

Convert to and back from an alist.

:(old-vector->{name} vector)

Reads in a vector of the form ''#({case-insensitive-name} {field0} ...)''.
This is only provided for compatibility with ''Scheme->C''.
Not yet implemented.

=== License ===

   Copyright (c) 2013, Andrei Barbu, Purdue University
   All rights reserved.

   Contact Andrei Barbu at andrei@0xab.com.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
   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 Lesser General Public License for more details.
   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see http://www.gnu.org/licenses.
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