5 unstable releases
0.3.1 | Apr 23, 2024 |
---|---|
0.3.0 | Apr 23, 2024 |
0.2.1 | Apr 22, 2024 |
0.2.0 | Apr 21, 2024 |
0.1.0 | Apr 21, 2024 |
#464 in Rust patterns
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36KB
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Indices
Zero allocation macros and methods for retrieving multiple mutable indices from a mutable slice safely. e.g.
let (two, four, three) = indices!(slice, 2, 4, 3);
Macros
All macros are zero allocation and allow retrieving a variable number of indices at runtime. Prefer macros when the number of indices are known at compile time. e.g.
fn main() {
struct Person {
first: String,
last: String,
}
let mut data = [
Person { first: "John".to_string(), last: "Doe".to_string() },
Person { first: "Jane".to_string(), last: "Smith".to_string() },
Person { first: "Alice".to_string(), last: "Johnson".to_string() },
Person { first: "Bob".to_string(), last: "Brown".to_string() },
Person { first: "Charlie".to_string(), last: "White".to_string() },
];
fn modify(data_slice: &mut [Person], index: usize){
let (four, func_provided, three) = indices!(data_slice, 4, index, 3);
four.last = "Black".to_string();
func_provided.first = "Jack".to_string();
three.last = "Jones".to_string();
}
let slice = data.as_mut_slice();
modify(slice, 1);
assert_eq!(data[4].last, "Black");
assert_eq!(data[1].first, "Jack");
assert_eq!(data[3].last, "Jones");
}
Methods
Methods allow for more dynamic runtime retrieval when the number of indices is unknown at compile time. e.g.
fn main() {
struct Node {
index: usize,
visted: usize,
edges: Vec<usize>,
message: String,
}
let mut graph = vec![
Node {
index: 0,
visted: usize::MAX,
edges: vec![1, 2],
message: String::new(),
},
Node {
index: 1,
visted: usize::MAX,
edges: vec![0, 2],
message: String::new(),
},
Node {
index: 2,
visted: usize::MAX,
edges: vec![3],
message: String::new(),
},
Node {
index: 4,
visted: usize::MAX,
edges: vec![1],
message: String::new(),
},
];
fn traverse_graph(graph: &mut [Node], current: usize, start: usize) -> bool {
if current == start {
return true;
}
let edges = graph[current].edges.clone();
let [mut current_node, mut edge_nodes] = indices_slices(graph, [&[current], &edges]);
for edge_node in edge_nodes.iter_mut() {
current_node[0].visted = current;
edge_node.message.push_str(&format!(
"This is Node `{}` Came from Node `{}`.",
edge_node.index, current_node[0].visted
));
}
for edge in edges {
if traverse_graph(graph, edge, start) {
return true;
}
}
return false;
}
traverse_graph(&mut *graph, 2, 0);
let answers = [
"This is Node `0` Came from Node `1`.",
"This is Node `1` Came from Node `3`.",
"This is Node `2` Came from Node `1`.",
"This is Node `4` Came from Node `2`.",
];
for (index, node) in graph.iter().enumerate() {
assert_eq!(&node.message, answers[index]);
}
}