While slicing a data collection, Rust allows us to omit either the start index or the end index or both from its syntax.
&variable[start_index..end_index];
For example :1. Omitting the Start Index of a Slice :
fn main() {
let numbers = [1, 2, 3, 4, 5];
// omit the start index
let slice = &numbers[..3];
println!("array = {:?}", numbers);
println!("slice = {:?}", slice);
}
Output :
array = [1, 2, 3, 4, 5]
slice = [1, 2, 3]
Here,
&numbers[..3] includes
..3 without the start index. This means the slice starts from index
0 and goes up to index
3 (exclusive). It is equivalent to
&numbers[0..3].
2. Omitting the End Index of a Slice :
fn main() {
let numbers = [1, 2, 3, 4, 5];
// omit the end index
let slice = &numbers[2..];
println!("array = {:?}", numbers);
println!("slice = {:?}", slice);
}
Output :
array = [1, 2, 3, 4, 5]
slice = [3, 4, 5]
Here,
&numbers[2..] includes
2.. without the end index. This means the slice starts from index
2 and goes up to index
5 (exclusive). It is equivalent to
&numbers[2..5].
3. Omitting both Start and End Index of a Slice :
fn main() {
let numbers = [1, 2, 3, 4, 5];
// omit the start index and the end index
// reference the whole array
let slice = &numbers[..];
println!("array = {:?}", numbers);
println!("slice = {:?}", slice);
}
Output :
array = [1, 2, 3, 4, 5]
slice = [1, 2, 3, 4, 5]
Here,
&numbers[..] includes .. without the start and end index. This means the slice starts from index 0 and goes up to index 5 (exclusive).
It is equivalent to
&numbers[0..5] which will produce the same slice and will reference the whole array.
