.. index:: assignvarsp
.. _assignvarsp/0:

**protocol**

``assignvarsp``
===============

Assignable variables (supporting backtracable assignement of non-variable terms) protocol.

| **Author:** Nobukuni Kino and Paulo Moura
| **Version:** 1.0
| **Date:** 2015/7/31

| **Compilation flags:**
|    ``static``


(no dependencies on other entities)


Public interface
----------------

.. raw:: html

   <div id="assignable/1"> </div>

.. index:: assignable/1
.. _assignvarsp/0::assignable/1:

``assignable/1``
^^^^^^^^^^^^^^^^

Makes Variable an assignable variable. Initial state will be empty.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``assignable(Variable)``
| **Mode and number of proofs:**
|    ``assignable(-assignvar)`` - ``one``

| **Exceptions:**
|    Variable is not a variable:
|        ``type_error(variable,Variable)``


.. raw:: html

   <div id="assignable/2"> </div>

.. index:: assignable/2
.. _assignvarsp/0::assignable/2:

``assignable/2``
^^^^^^^^^^^^^^^^

Makes Variable an assignable variable and sets its initial state to Value.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``assignable(Variable,Value)``
| **Mode and number of proofs:**
|    ``assignable(-assignvar,@nonvar)`` - ``one``

| **Exceptions:**
|    Variable is not a variable:
|        ``type_error(variable,Variable)``
|    Value is not instantiated:
|        ``instantiation_error``


.. raw:: html

   <div id="(<=)/2"> </div>

.. index:: (<=)/2
.. _assignvarsp/0::(<=)/2:

``(<=)/2``
^^^^^^^^^^

Sets the state of the assignable variable Variable to Value (initializing the variable if needed).

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``Variable<=Value``
| **Mode and number of proofs:**
|    ``(?assignvar)<=(@nonvar)`` - ``one``

| **Exceptions:**
|    Value is not instantiated:
|        ``instantiation_error``


.. raw:: html

   <div id="(=>)/2"> </div>

.. index:: (=>)/2
.. _assignvarsp/0::(=>)/2:

``(=>)/2``
^^^^^^^^^^

Unifies Value with the current state of the assignable variable Variable.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``Variable=>Value``
| **Mode and number of proofs:**
|    ``(+assignvar)=>(?nonvar)`` - ``zero_or_one``

| **Exceptions:**
|    Variable is not instantiated:
|        ``instantiation_error``


Protected interface
-------------------

(none)

Private predicates
------------------

(none)

Operators
---------

* ``op(100,xfx,<=) (public)``
* ``op(100,xfx,=>) (public)``


Remarks
-------

(none)

.. seealso::

   :ref:`assignvars <assignvars/0>`

