updating docs with single

Author: Jolanrensen

core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/ColumnsSelectionDsl.kt

@@ -63,6 +63,18 @@ class ColumnsSelectionDslTests : TestBase() {
                 it.any { it == "Alice" }
             }
         }
+
+        df.select {
+            "name".last {
+                it.any { it == "Alice" }
+            }
+        } shouldBe df.select { name.firstName }
+
+        df.select {
+            Person::name.last {
+                it.any { it == "Alice" }
+            }
+        } shouldBe df.select { name.firstName }
     }
 
     @Test
@@ -85,6 +97,18 @@ class ColumnsSelectionDslTests : TestBase() {
                 it.any { it == "Alice" }
             }
         }
+
+        df.select {
+            "name".single {
+                it.any { it == "Alice" }
+            }
+        } shouldBe df.select { name.firstName }
+
+        df.select {
+            Person::name.single {
+                it.any { it == "Alice" }
+            }
+        } shouldBe df.select { name.firstName }
     }
 
 }

core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/samples/api/Access.kt

@@ -820,6 +820,11 @@ class Access : TestBase() {
             group("name").last { it.name().endsWith("Name") }
         }
 
+        // find the single column inside a column group satisfying the condition
+        df.select {
+            Person::name.single { it.name().startsWith("first") }
+        }
+
         // depth-first-search traversal of all columns, excluding ColumnGroups from result
         df.select { allDfs() }
 

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/ColumnsSelectionDsl.kt

@@ -63,6 +63,18 @@ class ColumnsSelectionDslTests : TestBase() {
                 it.any { it == "Alice" }
             }
         }
+
+        df.select {
+            "name".last {
+                it.any { it == "Alice" }
+            }
+        } shouldBe df.select { name.firstName }
+
+        df.select {
+            Person::name.last {
+                it.any { it == "Alice" }
+            }
+        } shouldBe df.select { name.firstName }
     }
 
     @Test
@@ -85,6 +97,18 @@ class ColumnsSelectionDslTests : TestBase() {
                 it.any { it == "Alice" }
             }
         }
+
+        df.select {
+            "name".single {
+                it.any { it == "Alice" }
+            }
+        } shouldBe df.select { name.firstName }
+
+        df.select {
+            Person::name.single {
+                it.any { it == "Alice" }
+            }
+        } shouldBe df.select { name.firstName }
     }
 
 }

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/samples/api/Access.kt

@@ -820,6 +820,11 @@ class Access : TestBase() {
             group("name").last { it.name().endsWith("Name") }
         }
 
+        // find the single column inside a column group satisfying the condition
+        df.select {
+            Person::name.single { it.name().startsWith("first") }
+        }
+
         // depth-first-search traversal of all columns, excluding ColumnGroups from result
         df.select { allDfs() }
 

docs/StardustDocs/topics/ColumnSelectors.md

@@ -214,6 +214,11 @@ df.select {
     group("name").last { it.name().endsWith("Name") }
 }
 
+// find the single column inside a column group satisfying the condition
+df.select {
+    Person::name.single { it.name().startsWith("first") }
+}
+
 // depth-first-search traversal of all columns, excluding ColumnGroups from result
 df.select { allDfs() }