Samples: add some operations to do with the constructed ranges

libraries/stdlib/samples/test/samples/ranges/ranges.kt

@@ -18,6 +18,8 @@ package samples.ranges
 
 import samples.*
 import java.sql.Date
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
 
 class Ranges {
 
@@ -27,17 +29,27 @@ class Ranges {
         val end = Date.valueOf("2017-12-31")
         val range = start..end
         assertPrints(range, "2017-01-01..2017-12-31")
+
+        assertTrue(Date.valueOf("2017-05-27") in range)
+        assertFalse(Date.valueOf("2018-01-01") in range)
+        assertTrue(Date.valueOf("2018-01-01") !in range)
     }
 
     @Sample
     fun rangeFromDouble() {
         val range = 1.0..100.0
         assertPrints(range, "1.0..100.0")
+
+        assertTrue(3.14 in range)
+        assertFalse(100.1 in range)
     }
 
     @Sample
     fun rangeFromFloat() {
         val range = 1f..100f
         assertPrints(range, "1.0..100.0")
+
+        assertTrue(3.14f in range)
+        assertFalse(100.1f in range)
     }
 }