Map reduce example

mapreduce.rs

struct FooStore {
    value: i32,
}

struct ConcreteCompUnit<T> {
    unit: T,
}

enum CompUnit<T> {
    Concrete(ConcreteCompUnit<T>),
    Cluster(Vec<CompUnit<T>>),
}

impl<T> CompUnit<T> {
    fn map_reduce<O, MAPFN, REDUCEFN>(&self, map_fn: MAPFN, reduce_fn: REDUCEFN) -> O
    where
        MAPFN: Fn(&T) -> O + Clone,
        REDUCEFN: Fn(Vec<O>) -> O + Clone,
    {
        let values = match self {
            CompUnit::Concrete(concrete_unit) => {
                vec![map_fn(&concrete_unit.unit)]
            }
            CompUnit::Cluster(cluster) => cluster
                .iter()
                .map(|comp_unit| comp_unit.map_reduce(map_fn.clone(), reduce_fn.clone()))
                .collect(),
        };

        reduce_fn(values)
    }
}

fn main() {
    let unit = CompUnit::Cluster(vec![
        CompUnit::Concrete(ConcreteCompUnit {
            unit: FooStore { value: 12 },
        }),
        CompUnit::Cluster(vec![
            CompUnit::Concrete(ConcreteCompUnit {
                unit: FooStore { value: 14 },
            }),
            CompUnit::Concrete(ConcreteCompUnit {
                unit: FooStore { value: 16 },
            }),
        ]),
    ]);

    let sum = unit.map_reduce(|foo_store| foo_store.value, |values| values.iter().sum());

    println!("Sum: {}", sum);
}