[](https://crates.io/crates/carboxyl)
*Carboxyl* is a library for functional reactive programming in Rust, a
functional and composable approach to handle events in interactive
applications. Read more [in the docs…][docs]
[docs]: https://docs.rs/carboxyl/
## Usage example
Here is a simple example of how you can use the primitives provided by
*Carboxyl*. First of all, events can be sent into a *sink*. From a sink one can
create a *stream* of events. Streams can also be filtered, mapped and merged. A
*signal* is an abstraction of a value that may change over time. One can e.g.
hold the last event from a stream in a signal.
```rust
extern crate carboxyl;
fn main() {
let sink = carboxyl::Sink::new();
let stream = sink.stream();
let signal = stream.hold(3);
// The current value of the signal is initially 3
assert_eq!(signal.sample(), 3);
// When we fire an event, the signal get updated accordingly
sink.send(5);
assert_eq!(signal.sample(), 5);
}
```
One can also directly iterate over the stream instead of holding it in a
signal:
```rust
extern crate carboxyl;
fn main() {
let sink = carboxyl::Sink::new();
let stream = sink.stream();
let mut events = stream.events();
sink.send(4);
assert_eq!(events.next(), Some(4));
}
```
Streams and signals can be combined using various primitives. We can map a
stream to another stream using a function:
```rust
extern crate carboxyl;
fn main() {
let sink = carboxyl::Sink::new();
let stream = sink.stream();
let squares = stream.map(|x| x * x).hold(0);
sink.send(4);
assert_eq!(squares.sample(), 16);
}
```
Or we can filter a stream to create a new one that only contains events that
satisfy a certain predicate:
```rust
extern crate carboxyl;
fn main() {
let sink = carboxyl::Sink::new();
let stream = sink.stream();
let negatives = stream.filter(|&x| x < 0).hold(0);
// This won't arrive at the signal.
sink.send(4);
assert_eq!(negatives.sample(), 0);
// But this will!
sink.send(-3);
assert_eq!(negatives.sample(), -3);
}
```
There are a couple of other primitives to compose streams and signals:
- `merge` two streams of events of the same type.
- Make a `snapshot` of a signal, whenever a stream fires an event.
- `lift!` an ordinary function to a function on signals.
- `switch` between different signals using a signal containing a signal.
See the [documentation][docs] for details.
## License
Copyright 2014-2020 Carboxyl contributors.
This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at http://mozilla.org/MPL/2.0/.