Skip to main content

Range

std::ops::Range

The Range type in Rust represents an interval over a continuous sequence of values, typically numbers, but can work with any type that implements the PartialOrd and Step traits (like char for example). Ranges are used to iterate over a series of values or to define boundaries for slices and other operations.

Ranges are most commonly used in loops and indexing operations, and Rust provides multiple forms of ranges depending on the inclusivity or exclusivity of the endpoints.

Types of Ranges​

Rust provides several range types, each represented by a distinct syntax:

Range: Exclusive Range​

start..end

The Range type represents a half-open interval [start, end). It starts at start (inclusive) and goes up to, but does not include, end.

Example:

for i in 0..5 {
    println!("{}", i);  // prints 0, 1, 2, 3, 4
}

RangeInclusive: Inclusive Range​

start..=end

This range includes both the start and end values. It represents a fully-closed interval [start, end].

Example:

for i in 0..=5 {
    println!("{}", i);  // prints 0, 1, 2, 3, 4, 5
}

RangeFrom: Unbounded Range (From a start)​

start..

This range starts at start and continues indefinitely. It is useful for slicing when you want to include everything after a certain index.

Example:

let array = [1, 2, 3, 4, 5];
let slice = &array[2..];  // takes from index 2 to the end
assert_eq!(slice, &[3, 4, 5]);

RangeTo: Unbounded Range (Up to a point)​

..end

This range starts from the beginning and ends before end. It is exclusive, meaning it does not include end.

Example:

let array = [1, 2, 3, 4, 5];
let slice = &array[..3];  // takes up to (but not including) index 3
assert_eq!(slice, &[1, 2, 3]);

RangeToInclusive: Unbounded Range (Up to and including)​

..=end

This is similar to RangeTo, but it includes the end value as well.

Example:

let array = [1, 2, 3, 4, 5];
let slice = &array[..=3];  // takes up to and including index 3
assert_eq!(slice, &[1, 2, 3, 4]);

RangeFull: Full Range​

..

The RangeFull type is used when referring to the entire range of a collection. It is most often used in slicing.

Example:

let array = [1, 2, 3, 4, 5];
let slice = &array[..];  // takes the entire array
assert_eq!(slice, &[1, 2, 3, 4, 5]);

Traits and Methods​

Iterator  Trait​

All finite ranges implement the Iterator trait, making it easy to loop over them.

Example:

let sum: i32 = (1..5).sum();  // sums 1, 2, 3, 4
assert_eq!(sum, 10);

contains  Method​

You can use the contains method to check whether a value is within a range.

Example:

let range = 1..5;
assert!(range.contains(&3));  // true
assert!(!range.contains(&5)); // false (because it's exclusive)