Topic 3. Functions: default parameters, named arguments, extension functions; strings and string templates

Goal: learn to extract functions with explicit contracts, use default and named arguments, create extensions, and test text transformations.

Lecture contents

1. Function declarations and kinds — Declaration and calls · Unit, Nothing, and preconditions · Top-level and local functions
2. Parameters and arguments — Default parameters and named arguments · Vararg and array spreading
3. Recursion, infix functions, and extensions — Recursion and the call stack · Infix functions · Extension functions
4. Strings and string templates — String immutability and characters · Templates and multiline literals · Searching, slicing, and formatting · StringBuilder and incremental text construction
5. Regular expressions and testing — Regex: full matching and searching · Testing functions and text contracts

Practice and review

• Practice — 3 worked examples with complete code
• Tasks — 30 variants, each with tasks at three difficulty levels
• Summary — conclusions, self-check questions, and useful links