Concepts Learned Through 9 Programming Languages: Part 1 - Type Theory

Learning various programming languages is an essential process for broadening one's perspective on architecture design and implementing better code.

In particular, Null references can cause fatal bugs that undermine program stability, earning the nickname 'the billion-dollar mistake.' To prevent this, modern languages introduce Nullable types to catch problems at compile time.

Null handling methods differ by language as follows.

• Java: Manages the possibility of Null within the type domain through Optional<T>.
• C# & Kotlin: Explicitly denotes Nullable types through dedicated syntax (?).
• Rust & Scala: Defines an Option type and distinguishes states as None and Some(T).
• TypeScript: Expresses this using union types in the form string | null.

The reason Rust, Scala, and TypeScript share a similar structure is that they are all designed based on the Sum Type concept from type theory.