Why Rust is not a functional language

Rust is not a functional language despite borrowing some functional programming concepts. While it includes features like algebraic data types, pattern matching, and expression-oriented syntax, it lacks core functional characteristics such as guaranteed tail call elimination, functional purity, referential transparency, and truly first-class closures. Rust is fundamentally a systems programming language closer to C++ that strategically adopts proven FP solutions to address specific pain points like exception handling and ad-hoc polymorphism. The language's pervasive mutability, lack of purity guarantees, and imperative nature make it incompatible with functional programming paradigms, though these design choices align perfectly with its goal of being a pragmatic systems language.