Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/5616#discussion_r29216714
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathfuncs/unary.scala
---
@@ -0,0 +1,168 @@
+/*
+ * 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.spark.sql.catalyst.expressions.mathfuncs
+
+import org.apache.spark.sql.catalyst.expressions.{ExpectsInputTypes,
Expression, Row, UnaryExpression}
+import org.apache.spark.sql.types._
+
+/**
+ * A unary expression specifically for math functions. Math Functions
expect a specific type of
+ * input format, therefore these functions extend `ExpectsInputTypes`.
+ * @param name The short name of the function
+ */
+abstract class MathematicalExpression(name: String)
+ extends UnaryExpression with Serializable with ExpectsInputTypes {
+ self: Product =>
+ type EvaluatedType = Any
+
+ override def dataType: DataType = DoubleType
+ override def foldable: Boolean = child.foldable
+ override def nullable: Boolean = true
+ override def toString: String = s"$name($child)"
+}
+
+/**
+ * A unary expression specifically for math functions that take a `Double`
as input and return
+ * a `Double`.
+ * @param f The math function.
+ * @param name The short name of the function
+ */
+abstract class MathematicalExpressionForDouble(f: Double => Double, name:
String)
+ extends MathematicalExpression(name) { self: Product =>
+
+ override def expectedChildTypes: Seq[DataType] = Seq(DoubleType)
+
+ override def eval(input: Row): Any = {
+ val evalE = child.eval(input)
+ if (evalE == null) {
+ null
+ } else {
+ val result = f(evalE.asInstanceOf[Double])
+ if (result.isNaN) null else result
+ }
+ }
+}
+
+/**
+ * A unary expression specifically for math functions that take an `Int`
as input and return
+ * an `Int`.
+ * @param f The math function.
+ * @param name The short name of the function
+ */
+abstract class MathematicalExpressionForInt(f: Int => Int, name: String)
--- End diff --
looks like int/float/long are only used for signum. I think we can remove
the non-double signum, and just let the auto cast you added handle it for all
the types.
I also checked with @mengxr on this. Supporting only double as the output
type should be enough.
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