Expression.equalTo for MetricSpaces

Author: Torsten-Mumme

src/main/java/net/itarray/automotion/internal/properties/BinaryExpression.java

@@ -1,35 +1,42 @@
 package net.itarray.automotion.internal.properties;
 
 import net.itarray.automotion.internal.geometry.Direction;
-import net.itarray.automotion.internal.properties.Context;
+import net.itarray.automotion.internal.geometry.Scalar;
 import net.itarray.automotion.validation.properties.Expression;
 
 import java.util.function.BiFunction;
 
+import static net.itarray.automotion.internal.geometry.Scalar.scalar;
+
 public class BinaryExpression<L, R, T> implements Expression<T> {
 
     private final Expression<L> left;
     private final Expression<R> right;
-    private final BiFunction<L, R, T> operation;
+    private ContextBiFunction<L, R, T> contextBiFunction;
     private String descriptionFormat;
 
-    public BinaryExpression(Expression<L> left, Expression<R> right, BiFunction<L, R, T> operation, String descriptionFormat) {
+    public BinaryExpression(Expression<L> left, Expression<R> right, ContextBiFunction<L, R, T> contextBiFunction, String descriptionFormat) {
         this.left = left;
         this.right = right;
-        this.operation = operation;
         this.descriptionFormat = descriptionFormat;
+        this.contextBiFunction = contextBiFunction;
+    }
+
+    public BinaryExpression(Expression<L> left, Expression<R> right, BiFunction<L, R, T> operation, String descriptionFormat) {
+        this(left, right, (l, r, context) -> operation.apply(l, r), descriptionFormat);
     }
 
     @Override
     public T evaluateIn(Context context, Direction direction) {
-        return operation.apply(left.evaluateIn(context, direction), right.evaluateIn(context, direction));
+        return contextBiFunction.apply(left.evaluateIn(context, direction), right.evaluateIn(context, direction), context);
     }
 
     @Override
     public String getDescription(Context context, Direction direction) {
+        String toleranceDescription = context.getTolerance().equals(scalar(0)) ? "" : String.format(" with tolerance %s", context.getTolerance());
         return String.format(
                 descriptionFormat,
                 left.getDescription(context, direction),
-                right.getDescription(context, direction));
+                right.getDescription(context, direction)) + toleranceDescription;
     }
 }

src/main/java/net/itarray/automotion/internal/properties/ContextBiFunction.java

@@ -0,0 +1,6 @@
+package net.itarray.automotion.internal.properties;
+
+@FunctionalInterface
+public interface ContextBiFunction<L, R, T> {
+    T apply(L l, R r, Context context);
+}

src/main/java/net/itarray/automotion/validation/properties/Expression.java

@@ -1,11 +1,14 @@
 package net.itarray.automotion.validation.properties;
 
 import net.itarray.automotion.internal.geometry.Direction;
+import net.itarray.automotion.internal.geometry.MetricSpace;
 import net.itarray.automotion.internal.geometry.Scalar;
+import net.itarray.automotion.internal.properties.BinaryExpression;
 import net.itarray.automotion.internal.properties.Context;
 import net.itarray.automotion.internal.properties.PagePercentage;
 import net.itarray.automotion.internal.properties.PagePercentageOrPixels;
 import net.itarray.automotion.internal.properties.PercentReference;
+import net.itarray.automotion.internal.properties.PixelConstant;
 
 import static net.itarray.automotion.internal.geometry.Scalar.scalar;
 import static net.itarray.automotion.internal.properties.PercentReference.PAGE;
@@ -22,7 +25,6 @@ static PagePercentageOrPixels percentOrPixels(int constant) {
 
     static Expression<Scalar> percent(int percentage, PercentReference reference) {
         return percent(scalar(percentage), reference);
-
     }
 
     static Expression<Scalar> percent(Scalar percentage, PercentReference reference) {
@@ -33,6 +35,14 @@ static Expression<Scalar> percent(Scalar percentage, PercentReference reference)
         }
     }
 
+    static <V extends MetricSpace<V>> Expression<Boolean> equalTo(Expression<V> left, Expression<V> right) {
+        return new BinaryExpression<>(
+                left,
+                right,
+                (scalar, other, context) -> scalar.minus(other).norm().isLessOrEqualTo(context.getTolerance()),
+                "%s to be equal to %s");
+    }
+
     T evaluateIn(Context context, Direction direction);
 
     String getDescription(Context context, Direction direction);

src/test/java/net/itarray/automotion/tests/properties/EqualToTest.java

@@ -0,0 +1,49 @@
+package net.itarray.automotion.tests.properties;
+
+import net.itarray.automotion.internal.geometry.Direction;
+import net.itarray.automotion.internal.geometry.Scalar;
+import net.itarray.automotion.internal.properties.BinaryExpression;
+import net.itarray.automotion.internal.properties.PixelConstant;
+import net.itarray.automotion.validation.properties.Expression;
+import org.junit.Before;
+import org.junit.Ignore;
+import org.junit.Test;
+
+import static net.itarray.automotion.internal.geometry.Scalar.scalar;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EqualToTest {
+
+    private Expression<Boolean> expression;
+
+    @Before
+    public void setUp() {
+        expression = Expression.equalTo(
+                new PixelConstant(scalar(17)),
+                new PixelConstant(scalar(16)));
+    }
+
+    @Test
+    public void evaluatesToTheValueOfTheOperationAppliedToTheEvaluatedLeftAndRightExpressions() {
+        Boolean result = expression.evaluateIn(new TestContext(), Direction.RIGHT);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void evaluatesToTheValueOfTheOperationAppliedToTheEvaluatedLeftAndRightExpressionsTakingTheToleranceOfTheContextIntoAccount() {
+        Boolean result = expression.evaluateIn(new TestContext().withTolerance(scalar(1)), Direction.RIGHT);
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void describesItself() {
+        String description = expression.getDescription(new TestContext(), Direction.RIGHT);
+        assertThat(description).isEqualTo("17px to be equal to 16px");
+    }
+
+    @Test
+    public void describesItselfWithTolerance() {
+        String description = expression.getDescription(new TestContext().withTolerance(scalar(1)), Direction.RIGHT);
+        assertThat(description).isEqualTo("17px to be equal to 16px with tolerance 1");
+    }
+}

src/test/java/net/itarray/automotion/tests/properties/PagePercentageOrPixelsTest.java

@@ -26,8 +26,7 @@ public void evaluatesToItsValueInAnyPixelContext() {
 
     @Test
     public void evaluatesToItsValueInAnyPercentageContext() {
-        TestContext context = new TestContext();
-        context.setPixels(false);
+        TestContext context = new TestContext().withPixels(false);
         assertThat(condition.evaluateIn(context, Direction.RIGHT)).isEqualTo(scalar(104));
     }
 

src/test/java/net/itarray/automotion/tests/properties/TestContext.java

@@ -31,16 +31,18 @@ public boolean isPixels() {
         return pixels;
     }
 
-    public void setPixels(boolean pixels) {
+    public TestContext withPixels(boolean pixels) {
         this.pixels = pixels;
+        return this;
     }
 
     @Override
     public Scalar getTolerance() {
         return tolerance;
     }
 
-    public void setTolerance(Scalar tolerance) {
+    public TestContext withTolerance(Scalar tolerance) {
         this.tolerance = tolerance;
+        return this;
     }
 }