[GitHub] [spark] HyukjinKwon commented on a change in pull request #24232: [SPARK-27297] [SQL] Add higher order functions to scala API

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HyukjinKwon commented on a change in pull request #24232: [SPARK-27297] [SQL] Add higher order functions to scala API
URL: https://github.com/apache/spark/pull/24232#discussion_r269958689
 
 

 ##########
 File path: sql/core/src/main/scala/org/apache/spark/sql/functions.scala
 ##########
 @@ -3316,6 +3316,141 @@ object functions {
     ArrayExcept(col1.expr, col2.expr)
   }
 
+  private def expressionFunction(f: Column => Column)
+  : Expression => Expression =
+    x => f(Column(x)).expr
+
+  private def expressionFunction(f: (Column, Column) => Column)
+  : (Expression, Expression) => Expression =
+    (x, y) => f(Column(x), Column(y)).expr
+
+  private def expressionFunction(f: (Column, Column, Column) => Column)
+  : (Expression, Expression, Expression) => Expression =
+    (x, y, z) => f(Column(x), Column(y), Column(z)).expr
+
+  /**
+   * Returns an array of elements after applying a tranformation to each element
+   * in the input array.
+   *
+   * @group collection_funcs
+   */
+  def transform(column: Column, f: Column => Column): Column = withExpr {
+    HigherOrderUtils.transform(column.expr, expressionFunction(f))
+  }
+
+  /**
+   * Returns an array of elements after applying a tranformation to each element
+   * in the input array.
+   *
+   * @group collection_funcs
+   */
+  def transform(column: Column, f: (Column, Column) => Column): Column = withExpr {
+    HigherOrderUtils.transform(column.expr, expressionFunction(f))
+  }
+
+  /**
+   * Returns whether a predicate holds for one or more elements in the array.
+   *
+   * @group collection_funcs
+   */
+  def exists(column: Column, f: Column => Column): Column = withExpr {
 
 Review comment:
   But how do we support this in Java?

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