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https://issues.apache.org/jira/browse/TINKERPOP-1632?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16192093#comment-16192093
]
ASF GitHub Bot commented on TINKERPOP-1632:
-------------------------------------------
Github user twilmes commented on a diff in the pull request:
https://github.com/apache/tinkerpop/pull/729#discussion_r142801689
--- Diff:
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MathStep.java
---
@@ -0,0 +1,171 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.tinkerpop.gremlin.process.traversal.step.map;
+
+import net.objecthunter.exp4j.Expression;
+import net.objecthunter.exp4j.ExpressionBuilder;
+import org.apache.tinkerpop.gremlin.process.traversal.Pop;
+import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
+import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
+import org.apache.tinkerpop.gremlin.process.traversal.step.ByModulating;
+import org.apache.tinkerpop.gremlin.process.traversal.step.PathProcessor;
+import org.apache.tinkerpop.gremlin.process.traversal.step.Scoping;
+import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent;
+import
org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement;
+import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalRing;
+import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalUtil;
+import org.apache.tinkerpop.gremlin.structure.util.StringFactory;
+
+import java.util.HashSet;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * @author Marko A. Rodriguez (http://markorodriguez.com)
+ */
+public final class MathStep<S> extends MapStep<S, Double> implements
ByModulating, TraversalParent, Scoping, PathProcessor {
+
+ private static final String CURRENT = "_";
+ private final String equation;
+ private final Set<String> variables;
+ private TraversalRing<Object, Number> traversalRing = new
TraversalRing<>();
+ private Set<String> keepLabels;
+
+ public MathStep(final Traversal.Admin traversal, final String
equation) {
+ super(traversal);
+ this.equation = equation;
+ this.variables = MathStep.getVariables(this.equation);
+
+ }
+
+ @Override
+ protected Traverser.Admin<Double> processNextStart() {
+ return
PathProcessor.processTraverserPathLabels(super.processNextStart(),
this.keepLabels);
+ }
+
+ @Override
+ protected Double map(final Traverser.Admin<S> traverser) {
+ final Expression expression = new ExpressionBuilder(this.equation)
--- End diff --
Looking at the exp4j source, I think an `Expression` can be reused. If so,
this could be moved up into the constructor to save the repeated initialization
cost.
> Create a set of default functions
> ---------------------------------
>
> Key: TINKERPOP-1632
> URL: https://issues.apache.org/jira/browse/TINKERPOP-1632
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.3.0
> Reporter: Daniel Kuppitz
>
> We already have a a set of default BiFunctions / operators, that are not
> treated as lambdas. We should also have a bunch of simple functions, that can
> then be used in {{map()}} or {{sack()}} and that can be serialized as
> bytecode. For example:
> {noformat}
> ...map(sqrt)
> ...map(log)
> ...sack(sigmoid) // compute sigmoid of the current sack and update the
> sack
> ...sack(cos).by("x") // compute the cosine of the current element's "x" and
> assign / overwrite the current sack value
> {noformat}
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