From 1de7267256498e9a901129440d33e869bc970635 Mon Sep 17 00:00:00 2001
From: Jean-Guillaume Fages <jg.fages@cosling.com>
Date: Fri, 4 Aug 2023 23:55:40 +0200
Subject: [PATCH] pow and square refactoring

the constraint logic should be in the constraint factory only
---
 .../constraints/IIntConstraintFactory.java    | 20 +++++++++++++++++++
 .../discrete/arithmetic/BiArExpression.java   | 14 ++-----------
 .../discrete/arithmetic/UnArExpression.java   |  2 +-
 3 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/solver/src/main/java/org/chocosolver/solver/constraints/IIntConstraintFactory.java b/solver/src/main/java/org/chocosolver/solver/constraints/IIntConstraintFactory.java
index fc844e9b25..249422c8f2 100644
--- a/solver/src/main/java/org/chocosolver/solver/constraints/IIntConstraintFactory.java
+++ b/solver/src/main/java/org/chocosolver/solver/constraints/IIntConstraintFactory.java
@@ -546,6 +546,9 @@ default Constraint pow(IntVar base, int exponent, IntVar result) {
             b = mm.get(C - mid);
             return ref().times(a, b, Y);
             /*/
+            if (exponent == 2) {
+                return square(result, base);
+            }
             if ((exponent % 2) == 0) {
                 return new Constraint(ConstraintsName.POWER, new PropPowEven(result, base, exponent));
             } else {
@@ -555,6 +558,23 @@ default Constraint pow(IntVar base, int exponent, IntVar result) {
         }
     }
 
+    default Constraint pow(IntVar base, IntVar exponent, IntVar result) {
+        if (exponent.isInstantiated()) {
+            return pow(base, exponent.getValue(), result);
+        }
+        // table decomposition todo as intension constraint
+        Tuples tuples = new Tuples(true);
+        for (int val1 : base) {
+            for (int val2 : exponent) {
+                int res = (int) Math.pow(val1, val2);
+                if (result.contains(res)) {
+                    tuples.add(val1, val2, res);
+                }
+            }
+        }
+        return base.getModel().table(new IntVar[]{base, exponent, result}, tuples);
+    }
+
     //##################################################################################################################
     //TERNARIES ########################################################################################################
     //##################################################################################################################
diff --git a/solver/src/main/java/org/chocosolver/solver/expression/discrete/arithmetic/BiArExpression.java b/solver/src/main/java/org/chocosolver/solver/expression/discrete/arithmetic/BiArExpression.java
index 0e5b121e7e..f72cd84590 100644
--- a/solver/src/main/java/org/chocosolver/solver/expression/discrete/arithmetic/BiArExpression.java
+++ b/solver/src/main/java/org/chocosolver/solver/expression/discrete/arithmetic/BiArExpression.java
@@ -10,7 +10,6 @@
 package org.chocosolver.solver.expression.discrete.arithmetic;
 
 import org.chocosolver.solver.Model;
-import org.chocosolver.solver.constraints.extension.Tuples;
 import org.chocosolver.solver.variables.IntVar;
 import org.chocosolver.util.tools.VariableUtils;
 
@@ -106,19 +105,10 @@ public IntVar intVar() {
                     me = model.intVar(model.generateName("mod_exp_"), bounds[0], bounds[1]);
                     model.mod(v1, v2, me).post();
                     break;
-                case POW: // todo as intension constraint
+                case POW:
                     bounds = VariableUtils.boundsForPow(v1, v2);
                     me = model.intVar(model.generateName("pow_exp_"), bounds[0], bounds[1]);
-                    Tuples tuples = new Tuples(true);
-                    for(int val1 : v1){
-                        for(int val2 : v2){
-                            int res = (int)Math.pow(val1, val2);
-                            if(me.contains(res)) {
-                                tuples.add(val1, val2, res);
-                            }
-                        }
-                    }
-                    model.table(new IntVar[]{v1, v2, me}, tuples).post();
+                    model.pow(v1, v2, me).post();
                     break;
                 case MIN:
                     bounds = VariableUtils.boundsForMinimum(v1, v2);
diff --git a/solver/src/main/java/org/chocosolver/solver/expression/discrete/arithmetic/UnArExpression.java b/solver/src/main/java/org/chocosolver/solver/expression/discrete/arithmetic/UnArExpression.java
index 8390431fa2..c3644aebdd 100644
--- a/solver/src/main/java/org/chocosolver/solver/expression/discrete/arithmetic/UnArExpression.java
+++ b/solver/src/main/java/org/chocosolver/solver/expression/discrete/arithmetic/UnArExpression.java
@@ -90,7 +90,7 @@ public IntVar intVar() {
                 case SQR:
                     int[] bounds = VariableUtils.boundsForMultiplication(v, v);
                     me = model.intVar(model.generateName("sqr_exp_"), bounds[0], bounds[1]);
-                    model.times(v, v, me).post();
+                    model.square(me, v).post();
                     break;
                 default:
                     throw new UnsupportedOperationException("Unary arithmetic expressions does not support "+op.name());