# frappe - FRP library for Rust
[](https://travis-ci.org/wolfiestyle/frappe) [](https://crates.io/crates/frappe) [](https://docs.rs/frappe)
Frappe is a concurrent Event-Driven FRP library. It aims to provide a simple, efficient and
Rust-idiomatic way to write interactive applications in a declarative way.
Events are processed in streams, and they can be accumulated and read using signals.
Also stream events can be turned into futures using the `Stream::next` method, so you can
listen to them via async/await.
## Usage
```Rust
use frappe::Sink;
fn main() {
// values are sent from a sink..
let sink = Sink::new();
// ..into a stream chain
let stream = sink.stream().inspect(|a| println!("--sent: {}", a));
// `hold` creates a Signal that stores the last value sent to the stream
let last = stream.hold(0);
// stream callbacks receive a MaybeOwned<T> argument, so we need to deref the value
let sum = stream.fold(0, |acc, n| acc + *n);
let half_even = stream
// the methods filter, map, fold are analogous to Iterator operations
.filter(|n| n % 2 == 0)
.map(|n| *n / 2)
.fold(Vec::new(), |mut vec, n| {
vec.push(*n);
vec
}) // note: .collect::<Vec<_>>() does the same
.map(|v| format!("{:?}", v));
// we can send individual values
sink.send(6);
sink.send(42);
sink.send(-1);
// or multiple ones at once
sink.feed(10..15);
// `sample` gets a copy of the value stored in the signal
println!("last: {}", last.sample());
// printing a signal samples it
println!("sum: {}", sum);
println!("half_even: {}", half_even);
}
```
You can also check the [frappe-gtk examples](https://github.com/wolfiestyle/frappe-gtk/tree/master/examples)
for more complex usage examples on GUI applications.