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use std::marker::PhantomData;
pub struct Reader<'reader, R, A> {
run: Box<Fn(&R) -> A + 'reader>,
state_type: PhantomData<R>,
content_type: PhantomData<A>,
}
impl<'reader, R: 'reader, A: 'reader> Reader<'reader, R, A> {
pub fn new<F>(f: F) -> Reader<'reader, R, A>
where
F: Fn(&R) -> A + 'reader,
{
Reader {
run: Box::new(f),
state_type: PhantomData,
content_type: PhantomData,
}
}
pub fn run(&self, r: &R) -> A {
(self.run)(r)
}
pub fn map<B: 'reader, G>(self, f: G) -> Reader<'reader, R, B>
where
G: Fn(A) -> B + 'reader,
{
let h = move |s: &R| {
let a = (self.run)(s);
f(a)
};
Reader::new(h)
}
pub fn flat_map<B: 'reader, G>(self, f: G) -> Reader<'reader, R, B>
where
G: Fn(A) -> Reader<'reader, R, B> + 'reader,
{
let h = move |s: &R| {
let a = (self.run)(s);
(f(a).run)(s)
};
Reader::new(h)
}
}
#[cfg(test)]
mod tests {
use super::Reader;
#[derive(Debug)]
struct Connection {
x: i32,
}
fn get_user(id: i32) -> Reader<'static, Connection, i32> {
Reader::new(move |c: &Connection| id + c.x)
}
fn get_other(id: i32) -> Reader<'static, Connection, i32> {
Reader::new(move |c: &Connection| id + c.x)
}
#[test]
fn it_works() {
let conn = Connection { x: 9 };
let r = get_user(10).flat_map(|a| get_other(a + 1000));
let u = (r.run)(&conn);
println!("##### Result: {:?} ", u);
assert!(true);
}
}