Lectures

We break down the vararg parameter in Kotlin: why it exists, what a call with any number of arguments looks like (including f()), why inside the function it’s “almost an array” (you can use size, indices, and indexing), what limitations exist (only one vararg), and how to apply it in practice—from utilities like say()/ hint() to a simple debug().

We break down how to design signatures with vararg in Kotlin: why the “tail” of arguments is almost always placed at the end, what happens when vararg is not last (and why named arguments are then required), how default values and named args work together, and which rule applies when you skip parameters with default values. At the end— a cheat sheet on parameter order and a list of typical mistakes.

We break down why you can’t “just” pass an array into a vararg parameter, how the spread operator * works in Kotlin, how Array<T> differs from primitive arrays like IntArray, when toTypedArray() is required, and how to correctly forward vararg to other functions. At the end, you’ll find a set of common mistakes and quick rules so you don’t get stuck on type mismatches.

We break down why vararg functions must have an explicit contract for the “empty set”: when it makes sense to return a neutral value, when it’s better to provide a ...OrNull version and return null, and when it’s more correct to fail immediately via require(...). Along the way: common traps like xs [ 0 ], the Elvis operator ?:, the spread operator *, and examples from the mini app “Guess the Number”.

We break down how to design small console utilities in Kotlin so that the code in main reads like a script. We learn to use vararg for “sets” of strings and numbers, move configuration into parameters after vararg (via named arguments), and properly forward argument sets through the spread operator * when building utility chains ( printBlock, log, info/ error).