init research

dataframe/plugins/kotlin-dataframe/testData/box/infer.kt

@@ -0,0 +1,15 @@
+import org.jetbrains.kotlinx.dataframe.*
+import org.jetbrains.kotlinx.dataframe.annotations.*
+import org.jetbrains.kotlinx.dataframe.api.*
+import org.jetbrains.kotlinx.dataframe.io.*
+
+fun box(): String {
+    val df = dataFrameOf("a")(123)
+        .add("b", infer = Infer.Nulls) { 123 }
+        .convert { b }.with(infer = Infer.None) { it.toString() }
+        .select { a and b and expr(infer = Infer.Nulls) { 42 } }
+
+    val b: String = df.b[0]
+    val untitled: Int = df.untitled[0]
+    return "OK"
+}