Add DataRow receiver in DataFrame.map. Update docs.

Author: nikitinas

docs/StardustDocs/topics/map.md

@@ -7,9 +7,9 @@ Creates `List`, [DataFrame](DataFrame.md) or [DataColumn](DataColumn.md) with va
 **Map into `List`:**
 
 ```text
-map { transform }: List<T>
+map { rowExpression }: List<T>
 
-transform: (DataRow) -> T
+rowExpression: DataRow.(DataRow) -> Value
 ```
 
 <!---FUN map-->
@@ -23,7 +23,7 @@ df.map { 2021 - it.age }
 **Map into `DataColumn`:**
 
 ```text
-map(columnName) { rowExpression }: DataColumn
+mapToColumn(columnName) { rowExpression }: DataColumn
 
 rowExpression: DataRow.(DataRow) -> Value
 ```
@@ -61,7 +61,7 @@ See [row expressions](DataRow.md#row-expressions)
 **Map into `DataFrame`:**
 
 ```kotlin
-map { 
+mapToFrame { 
     columnMapping
     columnMapping
     ...

src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/map.kt

@@ -5,6 +5,7 @@ import org.jetbrains.kotlinx.dataframe.ColumnsContainer
 import org.jetbrains.kotlinx.dataframe.DataColumn
 import org.jetbrains.kotlinx.dataframe.DataFrame
 import org.jetbrains.kotlinx.dataframe.DataRow
+import org.jetbrains.kotlinx.dataframe.RowExpression
 import org.jetbrains.kotlinx.dataframe.Selector
 import org.jetbrains.kotlinx.dataframe.columns.ColumnAccessor
 import org.jetbrains.kotlinx.dataframe.columns.ColumnReference
@@ -46,7 +47,7 @@ public fun <T, R> DataColumn<T>.map(
 
 // region DataFrame
 
-public fun <T, R> DataFrame<T>.map(transform: (DataRow<T>) -> R): List<R> = rows().map(transform)
+public fun <T, R> DataFrame<T>.map(transform: RowExpression<T, R>): List<R> = rows().map { transform(it, it) }
 
 public inline fun <T, reified R> ColumnsContainer<T>.mapToColumn(
     name: String,