* Calls the specified function [block] with `this` value as its argument and returns its result.

tldr;

// using 'let' to convert from one type to another

val answerToUniverse = strBuilder.let {

it.append("Douglas Adams was right after all")

it.append("Life, the Universe and Everything")

42

}

// using 'let' to only print when str is not null

str?.let { print(it) }