Streamline use of toListOf by adding method to print data class definition of table schema

[holgerbrandl]

To streamline the transition from table rows to objects using df.toListOf<Something>(), it would be wonderful if kdf could print a schema (as data class definition) to standard out.

Currently, this is only possible by converting a data-frame into krangl-df (using https://github.com/holgerbrandl/kdfutils) and and using printDataClassSchema to print the schema:

import com.github.holgerbrandl.kdfutils.toKranglDF
import krangl.printDataClassSchema
import org.jetbrains.kotlinx.dataframe.api.toListOf
import org.jetbrains.kotlinx.dataframe.datasets.flightsData

fun main() {

    flightsData.toKranglDF().printDataClassSchema("FlightRecord")

    // note: the data class definition is created and printed by printDataClassSchema to stdout  
    data class FlightRecord(
        val year: Int,
        val month: Int,
        val day: Int,
        val dep_time: String?,
        val dep_delay: String?,
        val arr_time: String?,
        val arr_delay: String?,
        val carrier: String,
        val tailnum: String,
        val flight: Int,
        val origin: String,
        val dest: String,
        val air_time: String?,
        val distance: Int,
        val hour: String?,
        val minute: String?
    )

    val records = flightsData.toListOf<FlightRecord>()
    println(records.first())
}

which prints just

data class FlightRecord(val year: Int, val month: Int, val day: Int, val dep_time: Any?, val dep_delay: Any?, val arr_time: Any?, val arr_delay: Any?, val carrier: String, val tailnum: String, val flight: Int, val origin: String, val dest: String, val air_time: Any?, val distance: Int, val hour: Any?, val minute: Any?)

FlightRecord(year=2013, month=1, day=1, dep_time=517, dep_delay=2, arr_time=830, arr_delay=11, carrier=UA, tailnum=N14228, flight=1545, origin=EWR, dest=IAH, air_time=227, distance=1400, hour=5, minute=17)

Technically the approach suggested in #340 (comment) points into the same direction. However, having the ability to print a data-class definition of a data-frame would work more generally also in a simple kotlin jvm application without any compiler plugin or jupyter.

[Jolanrensen]

Solved by #763