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yap-6.3/packages/clpqr/clpqr.md

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Constraint Logic Programming over Rationals and Reals {#clpqr}
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=====================================================
YAP now uses the CLP(R) package developed by <em>Leslie De Koninck</em>,
K.U. Leuven as part of a thesis with supervisor Bart Demoen and daily
advisor Tom Schrijvers, and distributed with SWI-Prolog.
This CLP(R) system is a port of the CLP(Q,R) system of Sicstus Prolog
and YAP by Christian Holzbaur: Holzbaur C.: OFAI clp(q,r) Manual,
Edition 1.3.3, Austrian Research Institute for Artificial
Intelligence, Vienna, TR-95-09, 1995,
<http://www.ai.univie.ac.at/cgi-bin/tr-online?number+95-09> This
port only contains the part concerning real arithmetics. This manual
is roughly based on the manual of the above mentioned *CLP(QR)*
implementation.
Please note that the clpr library is <em>not</em> an
`autoload` library and therefore this library must be loaded
explicitely before using it:
~~~~~
:- use_module(library(clpr)).
~~~~~
### Solver Predicates {#CLPQR_Solver_Predicates}
The following predicates are provided to work with constraints:
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### Syntax of the predicate arguments {#CLPQR_Syntax}
The arguments of the predicates defined in the subsection above are
defined in the following table. Failing to meet the syntax rules will
result in an exception.
~~~~~
<Constraints> ---> <Constraint> \ single constraint \
| <Constraint> , <Constraints> \ conjunction \
| <Constraint> ; <Constraints> \ disjunction \
<Constraint> ---> <Expression> {<} <Expression> \ less than \
| <Expression> {>} <Expression> \ greater than \
| <Expression> {=<} <Expression> \ less or equal \
| {<=}(<Expression>, <Expression>) \ less or equal \
| <Expression> {>=} <Expression> \ greater or equal \
| <Expression> {=\=} <Expression> \ not equal \
| <Expression> =:= <Expression> \ equal \
| <Expression> = <Expression> \ equal \
<Expression> ---> <Variable> \ Prolog variable \
| <Number> \ Prolog number (float, integer) \
| +<Expression> \ unary plus \
| -<Expression> \ unary minus \
| <Expression> + <Expression> \ addition \
| <Expression> - <Expression> \ substraction \
| <Expression> * <Expression> \ multiplication \
| <Expression> / <Expression> \ division \
| abs(<Expression>) \ absolute value \
| sin(<Expression>) \ sine \
| cos(<Expression>) \ cosine \
| tan(<Expression>) \ tangent \
| exp(<Expression>) \ exponent \
| pow(<Expression>) \ exponent \
| <Expression> {^} <Expression> \ exponent \
| min(<Expression>, <Expression>) \ minimum \
| max(<Expression>, <Expression>) \ maximum \
~~~~~
### Use of unification {#CLPQR_Unification}
Instead of using the `{}/1` predicate, you can also use the standard
unification mechanism to store constraints. The following code samples
are equivalent:
+ Unification with a variable
~~~~~
{X =:= Y}
{X = Y}
X = Y
~~~~~
+ Unification with a number
~~~~~
{X =:= 5.0}
{X = 5.0}
X = 5.0
~~~~~
#### Non-Linear Constraints {#CLPQR_NonhYlinear_Constraints}
In this version, non-linear constraints do not get solved until certain
conditions are satisfied. We call these conditions the _isolation_ axioms.
They are given in the following table.
~~~~~
A = B * C when B or C is ground or // A = 5 * C or A = B * 4 \\
A and (B or C) are ground // 20 = 5 * C or 20 = B * 4 \\
A = B / C when C is ground or // A = B / 3
A and B are ground // 4 = 12 / C
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X = min(Y,Z) when Y and Z are ground or // X = min(4,3)
X = max(Y,Z) Y and Z are ground // X = max(4,3)
X = abs(Y) Y is ground // X = abs(-7)
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X = pow(Y,Z) when X and Y are ground or // 8 = 2 ^ Z
X = exp(Y,Z) X and Z are ground // 8 = Y ^ 3
X = Y ^ Z Y and Z are ground // X = 2 ^ 3
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X = sin(Y) when X is ground or // 1 = sin(Y)
X = cos(Y) Y is ground // X = sin(1.5707)
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X = tan(Y)
~~~~~