// Demonstrating several ways to build a vector containing a range of numbers.
// Each function shows a different style that experienced developers commonly use.
// Build a vector using the standard range syntax.
// This is concise, expressive, and uses built‑in iteration.
fn make_range_basic(start: i32, end: i32) -> Vec<i32> {
(start..end).collect()
}
// Build a vector using a manual loop.
// Clear and flexible; works well when adding extra logic.
fn make_range_loop(start: i32, end: i32) -> Vec<i32> {
let mut values: Vec<i32> = Vec::with_capacity((end - start) as usize);
for n in start..end {
values.push(n);
}
values
}
// Build a vector using iterator methods.
// Shows how to use map() and collect() together.
fn make_range_map(start: i32, end: i32) -> Vec<i32> {
(0..(end - start)).map(|i| start + i).collect()
}
// Build a vector using a generator‑style function (Rust iterators).
// Demonstrates custom iteration logic.
fn make_range_custom_iter(start: i32, end: i32) -> Vec<i32> {
struct RangeIter {
current: i32,
end: i32,
}
impl Iterator for RangeIter {
type Item = i32;
fn next(&mut self) -> Option<Self::Item> {
if self.current < self.end {
let value = self.current;
self.current += 1;
Some(value)
} else {
None
}
}
}
RangeIter { current: start, end }.collect()
}
// Print a vector for demonstration.
fn show(label: &str, values: &[i32]) {
println!("{}: {:?}", label, values);
}
fn main() {
let a: Vec<i32> = make_range_basic(1, 10);
let b: Vec<i32> = make_range_loop(1, 10);
let c: Vec<i32> = make_range_map(1, 10);
let d: Vec<i32> = make_range_custom_iter(1, 10);
show("basic range", &a);
show("loop", &b);
show("map", &c);
show("custom iterator", &d);
}
/*
run:
basic range: [1, 2, 3, 4, 5, 6, 7, 8, 9]
loop: [1, 2, 3, 4, 5, 6, 7, 8, 9]
map: [1, 2, 3, 4, 5, 6, 7, 8, 9]
custom iterator: [1, 2, 3, 4, 5, 6, 7, 8, 9]
*/
