Range. It is possible to create custom structs in Rust that store start and end indexes, but the Range struct can do this in a more standard way. We can use Range from std ops.
A generic type, Range can represent its start and end with a numeric type like usize. It is possible to use special, shortened syntax to create a Range.
Example. This program uses the Range struct within a struct, and as a local variable in the main function. We can get a slice from an array with a Range.
Part 1 The Example struct has a field of type Range(usize) and this means the Range has a start and end with usize values.
Part 2 We create an instance of the Example struct, specifying the start and end based on same-named local variables.
Part 3 We can use a shortened syntax to create a Range: we use 2 periods in between the start and end values.
Part 4 A range (even a local Range variable) can be used index an array or other slice and get a slice.
Part 5 For convenience, the Range struct provides a contains() function, and this can be used to see if a value falls within a range.
use std::ops::Range;
// Part 1: use Range as a field in a struct.
struct Example {
range: Range<usize>,
}
fn main() {
// Part 2: create struct containing range with 2 integers.
let start = 10;
let end = 20;
let example = Example {
range: Range { start, end },
};
println!("{:?}", example.range);
// Part 3: create struct containing range with simpler syntax.
let example2 = Example { range: start..end };
println!("{:?}", example2.range);
// Part 4: use inclusive range, and print values from array directly with named range.
let bytes = [100, 101, 102, 103, 104];
let range = 2..=4;
println!(
"{:?} {:?} {:?}",
range.clone(),
&bytes[range],
&bytes[2..=4]
);
// Part 5: see if range contains an integer.
let range2 = 5..15;
if range2.contains(&10) {
println!("Range contains 10!");
}
}10..20
10..20
2..=4 [102, 103, 104] [102, 103, 104]
Range contains 10!
Summary. Ranges are used frequently in Rust programs, and every time we use the short range syntax to get a slice, we are creating a range. Range is found in the standard library (std ops).
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