nvander1 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_r269973264
##########
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:
Actually a better idea would probably be to use java functional interfaces.
```java
@FuncitonalInterface
interface Function3[T1, T2, T3, R] {
R apply(T1 t1, T2 t2, T3 t3);
}
Column exists(Column column, Function3[Column, Column, Column, Column] f) =
...
```
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