span for Interval

Author: Torsten-Mumme

src/main/java/net/itarray/automotion/internal/geometry/Interval.java

@@ -2,8 +2,6 @@
 
 import java.util.Objects;
 
-import static java.lang.String.format;
-
 public class Interval {
     private final Scalar begin;
     private final Scalar end;
@@ -15,7 +13,14 @@ public Interval(Scalar begin, Scalar end) {
 
     @Override
     public String toString() {
-        return format("[%s, %s[", begin, end);
+        if (isEmpty()) {
+            return format("-", "-");
+        }
+        return format(begin.toString(), end.toString());
+    }
+
+    private String format(String begin, String end) {
+        return String.format("[%s, %s[", begin, end);
     }
 
     @Override
@@ -44,4 +49,16 @@ public Interval intersect(Interval interval) {
                 begin.max(interval.begin),
                 end.min(interval.end));
     }
+
+    public Interval span(Interval interval) {
+        if (isEmpty()) {
+            return interval;
+        }
+        if (interval.isEmpty()) {
+            return this;
+        }
+        return new Interval(
+                begin.min(interval.begin),
+                end.max(interval.end));
+    }
 }

src/test/java/net/itarray/automotion/tests/geometry/ContainedIntervalsTest.java

@@ -0,0 +1,30 @@
+package net.itarray.automotion.tests.geometry;
+
+import net.itarray.automotion.internal.geometry.Interval;
+import net.itarray.automotion.internal.geometry.Scalar;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ContainedIntervalsTest extends TwoIntervalsTest{
+
+    public Interval left() {
+        return new Interval(new Scalar(12), new Scalar(15));
+    }
+
+    public Interval right() {
+        return new Interval(new Scalar(20), new Scalar(20));
+    }
+
+    @Test
+    public void haveEmptyIntersection() {
+        assertThat(right().intersect(left()).isEmpty()).isTrue();
+    }
+
+    @Test
+    public void haveSpanEqualToTheNonEmptyInterval() {
+        Interval span = left();
+        assertThat(right().span(left())).isEqualTo(span);
+        assertThat(left().span(right())).isEqualTo(span);
+    }
+}

src/test/java/net/itarray/automotion/tests/geometry/DisjointIntervalsTest.java

@@ -0,0 +1,30 @@
+package net.itarray.automotion.tests.geometry;
+
+import net.itarray.automotion.internal.geometry.Interval;
+import net.itarray.automotion.internal.geometry.Scalar;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class DisjointIntervalsTest extends TwoIntervalsTest{
+
+    public Interval left() {
+        return new Interval(new Scalar(2), new Scalar(8));
+    }
+
+    public Interval right() {
+        return new Interval(new Scalar(10), new Scalar(17));
+    }
+
+    @Test
+    public void haveEmptyIntersection() {
+        assertThat(right().intersect(left()).isEmpty()).isTrue();
+    }
+
+    @Test
+    public void haveSpanFromSmallestBeginToLargestEnd() {
+        Interval span = new Interval(new Scalar(2), new Scalar(17));
+        assertThat(right().span(left())).isEqualTo(span);
+        assertThat(left().span(right())).isEqualTo(span);
+    }
+}

src/test/java/net/itarray/automotion/tests/geometry/EmptyAndNonEmptyIntervalsTest.java

@@ -0,0 +1,30 @@
+package net.itarray.automotion.tests.geometry;
+
+import net.itarray.automotion.internal.geometry.Interval;
+import net.itarray.automotion.internal.geometry.Scalar;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EmptyAndNonEmptyIntervalsTest extends TwoIntervalsTest{
+
+    public Interval left() {
+        return new Interval(new Scalar(12), new Scalar(15));
+    }
+
+    public Interval right() {
+        return new Interval(new Scalar(10), new Scalar(17));
+    }
+
+    @Test
+    public void haveIntersectionBeginningAtLargerStartAndEndingAtSmallerEnd() {
+        assertThat(right().intersect(left())).isEqualTo(new Interval(new Scalar(12), new Scalar(15)));
+    }
+
+    @Test
+    public void haveSpanFromSmallestBeginToLargestEnd() {
+        Interval span = new Interval(new Scalar(10), new Scalar(17));
+        assertThat(right().span(left())).isEqualTo(span);
+        assertThat(left().span(right())).isEqualTo(span);
+    }
+}

src/test/java/net/itarray/automotion/tests/geometry/IntervalTest.java

@@ -45,43 +45,4 @@ public void isNotEmpty() {
     public void isNotEqualToEmptyIntervals() {
         assertThat(interval).isNotEqualTo(new Interval(begin, begin));
     }
-
-    @Test
-    public void intersectionWithIntervalBeforeIsEmpty() {
-        Interval intersection = interval.intersect(new Interval(begin.minus(10), begin.minus(5)));
-        assertThat(intersection.isEmpty()).isTrue();
-    }
-
-    @Test
-    public void intersectionWithIntervalBeforeButTouchingIsEmpty() {
-        Interval intersection = interval.intersect(new Interval(begin.minus(10), begin));
-        assertThat(intersection.isEmpty()).isTrue();
-    }
-
-    @Test
-    public void intersectionWithIntervalContainingBeginIsNotEmpty() {
-        Interval intersection = interval.intersect(new Interval(begin.minus(10), begin.plus(1)));
-        assertThat(intersection.isEmpty()).isFalse();
-        assertThat(intersection).isEqualTo(new Interval(begin, begin.plus(1)));
-    }
-
-    @Test
-    public void intersectionWithIntervalContainingAPointJustBeforeEndIsNotEmpty() {
-        Interval intersection = interval.intersect(new Interval(end.minus(1), end.plus(10)));
-        assertThat(intersection.isEmpty()).isFalse();
-        assertThat(intersection).isEqualTo(new Interval(end.minus(1), end));
-    }
-
-    @Test
-    public void intersectionWithIntervalAfterIsEmpty() {
-        Interval intersection = interval.intersect(new Interval(end.plus(5), end.plus(10)));
-        assertThat(intersection.isEmpty()).isTrue();
-    }
-
-    @Test
-    public void intersectionWithIntervalAfterButTouchingIsEmpty() {
-        Interval intersection = interval.intersect(new Interval(end, end.plus(10)));
-        assertThat(intersection.isEmpty()).isTrue();
-    }
-
 }

src/test/java/net/itarray/automotion/tests/geometry/OverlappingIntervalsTest.java

@@ -0,0 +1,29 @@
+package net.itarray.automotion.tests.geometry;
+
+import net.itarray.automotion.internal.geometry.Interval;
+import net.itarray.automotion.internal.geometry.Scalar;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class OverlappingIntervalsTest extends TwoIntervalsTest{
+
+    public Interval left() {
+        return new Interval(new Scalar(2), new Scalar(12));
+    }
+
+    public Interval right() {
+        return new Interval(new Scalar(10), new Scalar(17));
+    }
+
+    @Test
+    public void haveIntersectionBeginningAtLargerStartAndEndingAtSmallerEnd() {
+        assertThat(right().intersect(left())).isEqualTo(new Interval(new Scalar(10), new Scalar(12)));
+    }
+    @Test
+    public void haveSpanFromSmallestBeginToLargestEnd() {
+        Interval span = new Interval(new Scalar(2), new Scalar(17));
+        assertThat(right().span(left())).isEqualTo(span);
+        assertThat(left().span(right())).isEqualTo(span);
+    }
+}

src/test/java/net/itarray/automotion/tests/geometry/TouchingIntervalsTest.java

@@ -0,0 +1,30 @@
+package net.itarray.automotion.tests.geometry;
+
+import net.itarray.automotion.internal.geometry.Interval;
+import net.itarray.automotion.internal.geometry.Scalar;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class TouchingIntervalsTest extends TwoIntervalsTest{
+
+    public Interval left() {
+        return new Interval(new Scalar(2), new Scalar(10));
+    }
+
+    public Interval right() {
+        return new Interval(new Scalar(10), new Scalar(17));
+    }
+
+    @Test
+    public void haveEmptyIntersection() {
+        assertThat(right().intersect(left()).isEmpty()).isTrue();
+    }
+
+    @Test
+    public void haveSpanFromSmallestBeginToLargestEnd() {
+        Interval span = new Interval(new Scalar(2), new Scalar(17));
+        assertThat(right().span(left())).isEqualTo(span);
+        assertThat(left().span(right())).isEqualTo(span);
+    }
+}

src/test/java/net/itarray/automotion/tests/geometry/TwoIntervalsTest.java

@@ -0,0 +1,24 @@
+package net.itarray.automotion.tests.geometry;
+
+import net.itarray.automotion.internal.geometry.Interval;
+import net.itarray.automotion.internal.geometry.Scalar;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public abstract class TwoIntervalsTest {
+
+    public abstract Interval left();
+
+    public abstract Interval right();
+
+    @Test
+    public void intersectIsSymmetric() {
+        assertThat(left().intersect(right())).isEqualTo(right().intersect(left()));
+    }
+
+    @Test
+    public void spanIsSymmetric() {
+        assertThat(left().span(right())).isEqualTo(right().span(left()));
+    }
+}