Is there a way to cut up a string by whitespace? - rust

Question

I'm trying to automatically split up a string by line, and then by whitespace for use in a Vec of Vec3.
v 0.500000 0.500000 -0.500000
v 0.500000 -0.500000 -0.500000
v 0.500000 0.500000 0.500000
v 0.500000 -0.500000 0.500000
v -0.500000 0.500000 -0.500000
v -0.500000 -0.500000 -0.500000
v -0.500000 0.500000 0.500000
v -0.500000 -0.500000 0.500000
vt 0.875000 0.500000
vt 0.625000 0.750000
vt 0.625000 0.500000
For example, given this sample, I would want to discard lines starting with "vt", and store the coordinates from the lines starting with "v".

Answer 1

You can use str::split_whitespace(). Here's a simple parser. It does not handle errors (instead panics), but it should be a good starting point:
#[derive(Debug)]
struct Vec3(f32, f32, f32);
fn main() {
let str = "v 0.500000 0.500000 -0.500000
v 0.500000 -0.500000 -0.500000
v 0.500000 0.500000 0.500000
v 0.500000 -0.500000 0.500000
v -0.500000 0.500000 -0.500000
v -0.500000 -0.500000 -0.500000
v -0.500000 0.500000 0.500000
v -0.500000 -0.500000 0.500000
vt 0.875000 0.500000
vt 0.625000 0.750000
vt 0.625000 0.500000";
let parsed = str
.split("\n")
.filter_map(|line| {
let mut parts = line.split_whitespace();
if parts.next().unwrap() == "v" {
Some(Vec3(
parts.next().unwrap().parse().unwrap(),
parts.next().unwrap().parse().unwrap(),
parts.next().unwrap().parse().unwrap(),
))
} else {
None
}
})
.collect::<Vec<Vec3>>();
dbg!(parsed);
}
Output:
[src/main.rs:33] parsed = [
Vec3(
0.5,
0.5,
-0.5,
),
Vec3(
0.5,
-0.5,
-0.5,
),
Vec3(
0.5,
0.5,
0.5,
),
Vec3(
0.5,
-0.5,
0.5,
),
Vec3(
-0.5,
0.5,
-0.5,
),
Vec3(
-0.5,
-0.5,
-0.5,
),
Vec3(
-0.5,
0.5,
0.5,
),
Vec3(
-0.5,
-0.5,
0.5,
),
]
Playground

Answer 2

Between the use of lines and split_whitespace, you can step through both of your iterators to do something like this to collect each row into its own vec3:
const data: &'static str = r"v 0.500000 0.500000 -0.500000
v 0.500000 -0.500000 -0.500000
v 0.500000 0.500000 0.500000
v 0.500000 -0.500000 0.500000
v -0.500000 0.500000 -0.500000
v -0.500000 -0.500000 -0.500000
v -0.500000 0.500000 0.500000
v -0.500000 -0.500000 0.500000
vt 0.875000 0.500000
vt 0.625000 0.750000
vt 0.625000 0.500000";
fn main() {
for row in data.lines() {
let mut cols = row.split_whitespace();
if Some("vt") != cols.next() {
let vec3 = (
cols.next().unwrap().parse::<f32>().unwrap(),
cols.next().unwrap().parse::<f32>().unwrap(),
cols.next().unwrap().parse::<f32>().unwrap(),
);
println!("{:?}", vec3);
}
}
}
You can simplify that a bit by using a crate to unpack the iterator into a tuple without needing to touch each element: Is there any way to unpack an iterator into a tuple?