isSome

IsSome is a predicate used to determine whether an option-like value represents the presence of a value rather than its absence. In Rust, the Option<T> type models an optional value with two variants: Some(T) and None. The is_some method, defined on Option<T>, returns true if the value is Some(_), and false if it is None. It borrows self immutably and does not move or consume the contained value.

In practice, is_some is a lightweight check that can be used in conditional expressions to decide whether further processing is possible without pattern matching. For example, let x = Some(5); x.is_some() evaluates to true. Let y: Option<i32> = None; y.is_some() evaluates to false.

Related concepts include is_none, the counterpart that returns true for None. To access the contained value, a programmer typically uses pattern matching (e.g., match or if let Some(v) = opt), or methods like unwrap, unwrap_or, or as_ref/as_mut to work with references without consuming the option.

IsSome is commonly used in conjunction with iterators and option-based logic in Rust, such as filtering or branching depending on the presence of a value. While it provides a quick boolean check, it does not reveal or extract the contained data; extracting the value requires additional pattern matching or helper methods.

Analogues in other languages exist: for instance, Haskell uses isJust for Maybe, and Java's Optional provides isPresent. However, is_some is a standard predicate in Rust’s Option<T> API.