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Merge pull request #55 from ferrous-systems/heapless_const_example

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radio-puzzle-help.md: add more hints to heapless constants
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Jorge Aparicio 2020-07-15 13:27:27 +00:00 committed by GitHub
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embedded-workshop-book/src/radio-puzzle-help.md
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@ -17,16 +17,18 @@ use heapless::consts::*; // defines U16, U32, U64... etc. to set the size of t
fn main() { fn main() {
// A hash map with a capacity of 16 key-value pairs allocated on the stack // A hash map with a capacity of 16 key-value pairs allocated on the stack
// note that U16 is a heapless constant, not Rust's u16
let mut my_map = FnvIndexMap::<_, _, U16>::new(); let mut my_map = FnvIndexMap::<_, _, U16>::new();
my_map.insert(b'A', b'~').unwrap(); my_map.insert(b'A', b'~').unwrap();
// A vector with a fixed capacity of 8 elements allocated on the stack // A vector with a fixed capacity of 8 elements allocated on the stack
// note that U8 is a heapless constant, not Rust's u8
let mut my_vec = Vec::<_, U8>::new(); let mut my_vec = Vec::<_, U8>::new();
my_vec.push(b'A').unwrap(); my_vec.push(b'A').unwrap();
} }
``` ```
If you haven't used a stack-allocated collection before note that you'll need to specify the capacity of the collection as a type parameter using one of the "type-level values" in the `heapless::consts` module. The [`heapless::IndexMap` documentation][indexMap] of the `heapless` crate has some usage examples, as does the [`heapless::Vec` documentation][vec]. If you haven't used a stack-allocated collection before note that you'll need to specify the capacity of the collection as a type parameter using one of the "type-level values" in the `heapless::consts` module (e.g. `U8`, `U64` etc.). The [`heapless::IndexMap` documentation][indexMap] of the `heapless` crate has some usage examples, as does the [`heapless::Vec` documentation][vec].
[indexMap]: https://docs.rs/heapless/0.5.5/heapless/struct.IndexMap.html [indexMap]: https://docs.rs/heapless/0.5.5/heapless/struct.IndexMap.html
[vec]: https://docs.rs/heapless/0.5.5/heapless/struct.Vec.html [vec]: https://docs.rs/heapless/0.5.5/heapless/struct.Vec.html