#246 Refactor Count/First/Last/FoldCat to OneToOneValueExpressions.

parsingdata · Aug 30, 2018 · 67d1c77 · 67d1c77
1 parent dede597
commit 67d1c77
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Showing 6 changed files with 101 additions and 110 deletions.
diff --git a/core/src/main/java/io/parsingdata/metal/expression/value/FoldCat.java b/core/src/main/java/io/parsingdata/metal/expression/value/FoldCat.java
@@ -16,14 +16,11 @@
 
 package io.parsingdata.metal.expression.value;
 
-import static java.math.BigInteger.ZERO;
-
 import static io.parsingdata.metal.data.Slice.createFromSource;
+import static java.math.BigInteger.ZERO;
 
-import java.util.Objects;
 import java.util.Optional;
 
-import io.parsingdata.metal.Util;
 import io.parsingdata.metal.data.ConcatenatedValueSource;
 import io.parsingdata.metal.data.ImmutableList;
 import io.parsingdata.metal.data.ParseState;
@@ -36,36 +33,17 @@
  * @see FoldLeft
  * @see Cat
  */
-public class FoldCat implements ValueExpression {
-
-    public final ValueExpression operand;
+public class FoldCat extends OneToOneValueExpression {
 
     public FoldCat(final ValueExpression operand) {
-        this.operand = operand;
-    }
-
-    @Override
-    public ImmutableList<Optional<Value>> eval(final ParseState parseState, final Encoding encoding) {
-        return ConcatenatedValueSource.create(operand.eval(parseState, encoding))
-            .flatMap(source -> createFromSource(source, ZERO, source.length))
-            .map(slice -> new ImmutableList<Optional<Value>>().add(Optional.of(new Value(slice, encoding))))
-            .orElseGet(() -> ImmutableList.create(Optional.empty()));
-    }
-
-    @Override
-    public String toString() {
-        return getClass().getSimpleName() + "(" + operand + ")";
-    }
-
-    @Override
-    public boolean equals(final Object obj) {
-        return Util.notNullAndSameClass(this, obj)
-            && Objects.equals(operand, ((FoldCat)obj).operand);
+        super(operand);
     }
 
     @Override
-    public int hashCode() {
-        return Objects.hash(getClass(), operand);
+    public Optional<Value> eval(final ImmutableList<Optional<Value>> list, final ParseState parseState, final Encoding encoding) {
+        return ConcatenatedValueSource.create(list)
+                .flatMap(source -> createFromSource(source, ZERO, source.length))
+                .map(slice -> new Value(slice, encoding));
     }
 
 }
diff --git a/core/src/main/java/io/parsingdata/metal/expression/value/OneToManyValueExpression.java b/core/src/main/java/io/parsingdata/metal/expression/value/OneToManyValueExpression.java
@@ -31,7 +31,8 @@
 import io.parsingdata.metal.encoding.Encoding;
 
 /**
- * Base class for {@link ValueExpression}s with one operand.
+ * Base class for {@link ValueExpression}s with one operand that evaluates
+ * to multiple values.
  * <p>
  * A OneToManyValueExpression implements a ValueExpression that has one
  * <code>operand</code> (a {@link ValueExpression}). The operand is first

diff --git a/core/src/main/java/io/parsingdata/metal/expression/value/OneToOneValueExpression.java b/core/src/main/java/io/parsingdata/metal/expression/value/OneToOneValueExpression.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2013-2016 Netherlands Forensic Institute
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.parsingdata.metal.expression.value;
+
+import static io.parsingdata.metal.Util.checkNotNull;
+
+import java.util.Objects;
+import java.util.Optional;
+
+import io.parsingdata.metal.Util;
+import io.parsingdata.metal.data.ImmutableList;
+import io.parsingdata.metal.data.ParseState;
+import io.parsingdata.metal.encoding.Encoding;
+
+/**
+ * Base class for {@link ValueExpression}s with one operand that evaluates
+ * to a single value.
+ * <p>
+ * A OneToOneValueExpression implements a ValueExpression that has one
+ * <code>operand</code> (a {@link ValueExpression}). The operand is first
+ * evaluated. If it evaluates to {@link Optional#empty()}, the result of the
+ * ValueExpression itself will be that as well.
+ * <p>
+ * To implement a OneToOneValueExpression, only the
+ * {@link #eval(ImmutableList, ParseState, Encoding)} must
+ * be implemented, handling the case of evaluating a list of values. This
+ * base class takes care of evaluating the operand and handling list
+ * semantics.
+ *
+ * @see BinaryValueExpression
+ */
+public abstract class OneToOneValueExpression implements ValueExpression {
+
+    public final ValueExpression operand;
+
+    public OneToOneValueExpression(final ValueExpression operand) {
+        this.operand = checkNotNull(operand, "operand");
+    }
+
+    @Override
+    public ImmutableList<Optional<Value>> eval(final ParseState parseState, final Encoding encoding) {
+        return ImmutableList.create(eval(operand.eval(parseState, encoding), parseState, encoding));
+    }
+
+    public abstract Optional<Value> eval(final ImmutableList<Optional<Value>> list, final ParseState parseState, final Encoding encoding);
+
+    @Override
+    public String toString() {
+        return getClass().getSimpleName() + "(" + operand + ")";
+    }
+
+    @Override
+    public boolean equals(final Object obj) {
+        return Util.notNullAndSameClass(this, obj)
+                && Objects.equals(operand, ((OneToOneValueExpression)obj).operand);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(getClass(), operand);
+    }
+
+}
diff --git a/core/src/main/java/io/parsingdata/metal/expression/value/reference/Count.java b/core/src/main/java/io/parsingdata/metal/expression/value/reference/Count.java
@@ -16,56 +16,34 @@
 
 package io.parsingdata.metal.expression.value.reference;
 
-import static io.parsingdata.metal.Util.checkNotNull;
-
-import java.util.Objects;
 import java.util.Optional;
 
-import io.parsingdata.metal.Util;
 import io.parsingdata.metal.data.ImmutableList;
 import io.parsingdata.metal.data.ParseState;
 import io.parsingdata.metal.encoding.Encoding;
 import io.parsingdata.metal.encoding.Sign;
 import io.parsingdata.metal.expression.value.ConstantFactory;
+import io.parsingdata.metal.expression.value.OneToOneValueExpression;
 import io.parsingdata.metal.expression.value.Value;
 import io.parsingdata.metal.expression.value.ValueExpression;
 
 /**
  * A {@link ValueExpression} that represents the amount of {@link Value}s
  * returned by evaluating its <code>operand</code>.
  */
-public class Count implements ValueExpression {
-
-    public final ValueExpression operand;
+public class Count extends OneToOneValueExpression {
 
     public Count(final ValueExpression operand) {
-        this.operand = checkNotNull(operand, "operand");
+        super(operand);
     }
 
     @Override
-    public ImmutableList<Optional<Value>> eval(final ParseState parseState, final Encoding encoding) {
-        final ImmutableList<Optional<Value>> values = operand.eval(parseState, encoding);
-        return ImmutableList.create(Optional.of(fromNumeric(values.size)));
+    public Optional<Value> eval(final ImmutableList<Optional<Value>> list, final ParseState parseState, final Encoding encoding) {
+        return Optional.of(fromNumeric(list.size));
     }
 
     private static Value fromNumeric(final long length) {
         return ConstantFactory.createFromNumeric(length, new Encoding(Sign.SIGNED));
     }
 
-    @Override
-    public String toString() {
-        return getClass().getSimpleName() + "(" + operand + ")";
-    }
-
-    @Override
-    public boolean equals(final Object obj) {
-        return Util.notNullAndSameClass(this, obj)
-            && Objects.equals(operand, ((Count)obj).operand);
-    }
-
-    @Override
-    public int hashCode() {
-        return Objects.hash(getClass(), operand);
-    }
-
 }
diff --git a/core/src/main/java/io/parsingdata/metal/expression/value/reference/First.java b/core/src/main/java/io/parsingdata/metal/expression/value/reference/First.java
@@ -18,55 +18,34 @@
 
 import static io.parsingdata.metal.Trampoline.complete;
 import static io.parsingdata.metal.Trampoline.intermediate;
-import static io.parsingdata.metal.Util.checkNotNull;
 
-import java.util.Objects;
 import java.util.Optional;
 
 import io.parsingdata.metal.Trampoline;
-import io.parsingdata.metal.Util;
 import io.parsingdata.metal.data.ImmutableList;
 import io.parsingdata.metal.data.ParseState;
 import io.parsingdata.metal.encoding.Encoding;
+import io.parsingdata.metal.expression.value.OneToOneValueExpression;
 import io.parsingdata.metal.expression.value.Value;
 import io.parsingdata.metal.expression.value.ValueExpression;
 
 /**
  * A {@link ValueExpression} that represents the first {@link Value} returned
  * by evaluating its <code>operand</code>.
  */
-public class First implements ValueExpression {
-
-    public final ValueExpression operand;
+public class First extends OneToOneValueExpression {
 
     public First(final ValueExpression operand) {
-        this.operand = checkNotNull(operand, "operand");
+        super(operand);
     }
 
     @Override
-    public ImmutableList<Optional<Value>> eval(final ParseState parseState, final Encoding encoding) {
-        final ImmutableList<Optional<Value>> list = operand.eval(parseState, encoding);
-        return list.isEmpty() ? list : ImmutableList.create(getFirst(list).computeResult());
+    public Optional<Value> eval(final ImmutableList<Optional<Value>> list, final ParseState parseState, final Encoding encoding) {
+        return list.isEmpty() ? Optional.empty() : getFirst(list).computeResult();
     }
 
     private Trampoline<Optional<Value>> getFirst(final ImmutableList<Optional<Value>> values) {
         return values.tail.isEmpty() ? complete(() -> values.head) : intermediate(() -> getFirst(values.tail));
     }
 
-    @Override
-    public String toString() {
-        return getClass().getSimpleName() + "(" + operand + ")";
-    }
-
-    @Override
-    public boolean equals(final Object obj) {
-        return Util.notNullAndSameClass(this, obj)
-            && Objects.equals(operand, ((First)obj).operand);
-    }
-
-    @Override
-    public int hashCode() {
-        return Objects.hash(getClass(), operand);
-    }
-
 }
diff --git a/core/src/main/java/io/parsingdata/metal/expression/value/reference/Last.java b/core/src/main/java/io/parsingdata/metal/expression/value/reference/Last.java
@@ -16,50 +16,28 @@
 
 package io.parsingdata.metal.expression.value.reference;
 
-import static io.parsingdata.metal.Util.checkNotNull;
-
-import java.util.Objects;
 import java.util.Optional;
 
-import io.parsingdata.metal.Util;
 import io.parsingdata.metal.data.ImmutableList;
 import io.parsingdata.metal.data.ParseState;
 import io.parsingdata.metal.encoding.Encoding;
+import io.parsingdata.metal.expression.value.OneToOneValueExpression;
 import io.parsingdata.metal.expression.value.Value;
 import io.parsingdata.metal.expression.value.ValueExpression;
 
 /**
  * A {@link ValueExpression} that represents the last {@link Value} returned
  * by evaluating its <code>operand</code>.
  */
-public class Last implements ValueExpression {
-
-    public final ValueExpression operand;
+public class Last extends OneToOneValueExpression {
 
     public Last(final ValueExpression operand) {
-        this.operand = checkNotNull(operand, "operand");
-    }
-
-    @Override
-    public ImmutableList<Optional<Value>> eval(final ParseState parseState, final Encoding encoding) {
-        final ImmutableList<Optional<Value>> list = operand.eval(parseState, encoding);
-        return list.isEmpty() ? list : ImmutableList.create(list.head);
-    }
-
-    @Override
-    public String toString() {
-        return getClass().getSimpleName() + "(" + operand + ")";
-    }
-
-    @Override
-    public boolean equals(final Object obj) {
-        return Util.notNullAndSameClass(this, obj)
-            && Objects.equals(operand, ((Last)obj).operand);
+        super(operand);
     }
 
     @Override
-    public int hashCode() {
-        return Objects.hash(getClass(), operand);
+    public Optional<Value> eval(final ImmutableList<Optional<Value>> list, final ParseState parseState, final Encoding encoding) {
+        return list.isEmpty() ? Optional.empty() : list.head;
     }
 
 }