..
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   Copyright 1998-2020 Paulo Moura <pmoura@logtalk.org>

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
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   See the License for the specific language governing permissions and
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.. index:: pair: discontiguous/1; Directive
.. _directives_discontiguous_1:

discontiguous/1
===============

Description
-----------

::

   discontiguous(Name/Arity)
   discontiguous((Name/Arity, ...))
   discontiguous([Name/Arity, ...])

   discontiguous(Name//Arity)
   discontiguous((Name//Arity, ...))
   discontiguous([Name//Arity, ...])

Declares discontiguous predicates and discontiguous grammar rule
non-terminals. The use of this directive should be avoided as not all
:term:`backend Prolog compilers <backend Prolog compiler>` support
discontiguous predicates.

.. warning::

   Some backend Prolog compilers declare ``discontiguous`` as an operator
   for a lighter syntax. But this makes the code non-portable and is
   a practice best avoided.

Template and modes
------------------

::

   discontiguous(+predicate_indicator_term)
   discontiguous(+non_terminal_indicator_term)

Examples
--------

::

   :- discontiguous(counter/1).

   :- discontiguous((lives/2, works/2)).

   :- discontiguous([db/4, key/2, file/3]).
