More next randoms.

mihxil-algebra/src/main/java/org/meeuw/math/abstractalgebra/dihedral/DihedralSymmetry.java

@@ -4,6 +4,7 @@
 
 import java.util.function.UnaryOperator;
 
+import org.meeuw.math.Utils;
 import org.meeuw.math.abstractalgebra.GroupElement;
 import org.meeuw.math.abstractalgebra.dim2.Matrix2;
 import org.meeuw.math.abstractalgebra.dim2.Vector2;
@@ -94,7 +95,7 @@ public String toString() {
     }
 
     public Matrix2 asMatrix2() {
-        double phi = 2 * Math.PI * k / group.n;
+        double phi = Utils.Math_2PI * k / group.n;
         double cos = Math.cos(phi);
         double sin = Math.sin(phi);
         if (symmetry == r) {

mihxil-algebra/src/main/java/org/meeuw/math/abstractalgebra/dim3/RotationGroup.java

@@ -21,6 +21,8 @@
 import org.meeuw.math.abstractalgebra.*;
 import org.meeuw.math.abstractalgebra.reals.RealField;
 
+import static org.meeuw.math.Utils.Math_2PI;
+
 /**
  * SO(3) group. A non-abelian multiplicative group.
  *
@@ -42,9 +44,9 @@ public Rotation one() {
 
     @Override
      public Rotation nextRandom(Random r) {
-        Rotation rx = Rotation.Rx(r.nextDouble(0, 2 * Math.PI));
-        Rotation ry = Rotation.Ry(r.nextDouble(0, 2 * Math.PI));
-        Rotation rz = Rotation.Rz(r.nextDouble(0, 2 * Math.PI));
+        Rotation rx = Rotation.Rx(r.nextDouble(0d, Math_2PI));
+        Rotation ry = Rotation.Ry(r.nextDouble(0d, Math_2PI));
+        Rotation rz = Rotation.Rz(r.nextDouble(0d, Math_2PI));
         return rx.times(ry).times(rz);
     }
 

mihxil-algebra/src/main/java/org/meeuw/math/abstractalgebra/permutations/PermutationGroup.java

@@ -66,6 +66,16 @@ public Permutation one() {
         return one;
     }
 
+    @Override
+    public Permutation nextRandom(Random random) {
+        List<Integer> list = new ArrayList<>(degree);
+        for (int i = 0; i < degree; i++) {
+            list.add(i);
+        }
+        Collections.shuffle(list, random);
+        return Permutation.zeroOffset(list.stream().mapToInt(i -> i).toArray());
+    }
+
     @Override
     public Cardinality getCardinality() {
         return Cardinality.of(IntegerUtils.factorial(degree));

mihxil-algebra/src/main/java/org/meeuw/math/abstractalgebra/vectorspace/NVectorSpace.java

@@ -19,6 +19,7 @@
 
 import java.lang.reflect.Array;
 import java.util.Map;
+import java.util.Random;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Stream;
 
@@ -86,9 +87,14 @@ public Field<E> getField() {
         return field;
     }
 
+    @SuppressWarnings("unchecked")
     @Override
-    public boolean equals(Object o) {
-        return this == o;
+    public NVector<E> nextRandom(Random random) {
+         E[] elements = (E[]) Array.newInstance(field.getElementClass(), dimension);
+        for (int i = 0; i < dimension; i ++) {
+            elements[i] = field.nextRandom(random);
+        }
+        return new NVector<>(elements);
     }
 
     @Override

mihxil-algebra/src/test/java/org/meeuw/test/math/abstractalgebra/dim3/RotationTest.java

@@ -23,11 +23,12 @@
 import org.meeuw.math.abstractalgebra.dim3.FieldVector3;
 import org.meeuw.math.abstractalgebra.dim3.Rotation;
 import org.meeuw.math.abstractalgebra.reals.RealNumber;
-import org.meeuw.theories.abstractalgebra.MultiplicativeGroupTheory;
 import org.meeuw.math.text.TextUtils;
+import org.meeuw.theories.abstractalgebra.MultiplicativeGroupTheory;
 
 import static java.lang.Math.PI;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.meeuw.math.Utils.Math_2PI;
 import static org.meeuw.math.abstractalgebra.dim3.FieldVector3.of;
 import static org.meeuw.math.abstractalgebra.dim3.Rotation.*;
 import static org.meeuw.math.uncertainnumbers.CompareConfiguration.withLooseEquals;
@@ -90,7 +91,7 @@ public void determinantShouldBeOne(@ForAll(ELEMENTS) Rotation r) {
 
     @Override
     public Arbitrary<Rotation> elements() {
-        return Arbitraries.doubles().ofScale(20).between(0, 2d * PI)
+        return Arbitraries.doubles().ofScale(20).between(0, Math_2PI)
             .tuple3()
             .map(t -> Rx(t.get1()).times(Ry(t.get2())).times(Rz(t.get3())))
             ;

mihxil-math/src/main/java/org/meeuw/math/Utils.java

@@ -33,4 +33,6 @@ private Utils() {}
     public static final String e = "2.7182818284590452353602874713526624977572470936999595749669676277240766303535475945713821785251664274274663919320030599218174135966290435729003342952605956307381323286279434907632338298807531952510190115738341879307021540891499348841675092447614606680822648001684774118537423454424371075390777449920695517027618386062613313845830007520449338265602976067371132007093287091274437470472306969772093101416928368190255151086574637721112523897844250569536967707854499699679468644549059879316368892300987931277361782154249992295763514822082698951936680331825288693984964651058209392398294887933203625094431173012381970684161403970198376793206832823764648042953118023287825098194558153017567173613320698112509961818815930416903515988885193458072738667385894228792284998920868058257492796104841984443634632449684875602336248270419786232090021609902353043699418491463140934317381436405462531520961836908887070167683964243781405927145635490613031072085103837505101157477041718986106873969655212671546889570350354";
 
 
+    public static final double Math_2PI = 2d * Math.PI;
+
 }

mihxil-math/src/main/java/org/meeuw/math/abstractalgebra/AlgebraicStructure.java

@@ -215,7 +215,7 @@ default E[] newArray(int i) {
      */
     @Override
     default  E nextRandom(Random random) {
-        throw new UnsupportedOperationException("nextRandom not implemented in " + this.getClass() + " " + this);
+         throw new UnsupportedOperationException("nextRandom not implemented in " + this.getClass() + " " + this);
     }