Slices

Published Nov 28, 2023
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Slices in Rust are references to consecutive elements in memory, allowing you to reference parts of a collection without copying the entire data, providing a view into arrays, vectors, or other sequences for focused data manipulation.

Syntax

The syntax for a slice in Rust is represented as &[T], where T is the element type.

 let my_slice = &data_structure[start_index..end_index];
  • data_structure: Refers to the chosen data structure.
  • start_index: Denotes the starting point.
  • end_index: Represents one past the last element of the slice.

Note: This syntax is applicable to many forms of data, enabling the creation of slices from different collections.

Example

fn main() {
let my_array = [1, 2, 3, 4, 5];
let my_slice = &my_array[1..4];
println!("Slice: {:?}", my_slice);
}

The above example will result in the following output:

Slice: [2, 3, 4]

Omit Indexes of a Rust Slice

When creating a slice in Rust, one can include both the start and end index or one can include only one of the indexes.

Excluding the Start Index of a Slice

This example illustrates how to create a slice from the start of the array to index 3 (excluding the element at index 3):

fn main() {
let my_arr = [1, 2, 3, 4, 5];
let my_slice = &my_arr[..3];
println!("Slice without start index: {:?}", my_slice);
}

The above example will result in the following output:

Slice without start index: [1, 2, 3]

Excluding the End Index of a Slice

This example demonstrates how to create a slice from index 2 to the end of the array:

fn main() {
let my_arr = [1, 2, 3, 4, 5];
let my_slice = &my_arr[2..];
println!("Slice without end index: {:?}", my_slice);
}

The above example will result in the following output:

Slice without end index: [3, 4, 5]

Excluding both the Start and End Index of a Slice

This example displays the complete slice of the array, including all elements:

fn main() {
let my_arr = [1, 2, 3, 4, 5];
let my_slice = &my_arr[..];
println!("Complete slice: {:?}", my_slice);
}

The above example will result in the following output:

Complete slice: [1, 2, 3, 4, 5]

Rust’s Mutable Slices

In Rust, when a slice is designated as mutable, the alteration of the elements within the slice is allowed. The creation of a mutable slice is done by using the &mut keyword.

Mutable Slice Syntax

let slice = &mut data_structure[start_index..end_index];

Mutable Slice Example

The following example demonstrates how to modify an element in a mutable slice. In this case, the second element of the slice is changed from 3 to 10:

fn main() {
let mut my_vec = vec![1, 2, 3, 4, 5];
let my_slice = &mut my_vec[1..4];
my_slice[1] = 10; // Modifying the second element of the slice
println!("Modified Slice: {:?}", my_slice);
}

The above example will result in the following output:

Modified Slice: [2, 10, 4]

Note: Slices are often used in Rust for tasks like substring extraction, working with subarrays, and allowing multiple parts of a data structure to be manipulated separately without copying the entire data. They offer a flexible and memory-efficient way to handle data subsets.

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