lukeknxt

data class Wrapper(val id: String)
val ids = listOf("id1", "id2")
listOf(
    Wrapper("id1").id,
    Wrapper("id2")
).forEach { someId -> // inferred as Any
    val result = ids.find { it == someId }
    // id2 will never be found, but the compiler won't tell you
}

lukeknxt

"""
Use-case: automate clones in Databricks for dev testing similar to Snowflake's zero-copy clone.

This doesn't use the Catalog API as that may rely on cred passthrough
- https://docs.microsoft.com/en-us/azure/databricks/security/credential-passthrough/adls-passthrough

`py4j.security.Py4JSecurityException: method ... is not whitelisted on class org.apache.spark.sql.catalog.Table`
"""

prefixes = ["layer_a", "layer_b"] # prefix matching on schemas to copy over for layers

lukeknxt

enum E {
  A = "A",
  B = "B",
}

const yep: "A" = E.A;
const yep2: E = E.A;
const nope: E = "A"; // why though

lukeknxt

interface Service {
  update(obj: { id?: string }): void;
  // changing this to a function type `update: (obj: {id?: string}) => void` works
  // and causes the implementation not to type-check
}

class ServiceImpl implements Service {
  // somehow this is a valid implementation
  update(obj: { id: string }): void {
    // `id` can never be undefined or null here according to the type system

lukeknxt

// scala version
def mostFrequent(arr: Array[Int]): Int = {
  arr.groupBy(identity).maxBy(_._2.size)._1
}

// java version (from https://www.geeksforgeeks.org/frequent-element-array/) 
import java.util.HashMap; 
import java.util.Map; 
import java.util.Map.Entry;