Function count 

pub fn count<A>() -> CountCollector<A>

Creates a collector that counts entities.

Example

use solverforge_scoring::stream::collector::{count, UniCollector, Accumulator};

let collector = count::<i32>();
let mut acc = collector.create_accumulator();

acc.accumulate(&collector.extract(&1));
acc.accumulate(&collector.extract(&2));
acc.accumulate(&collector.extract(&3));
assert_eq!(acc.get(), 3);

acc.retract(&collector.extract(&2));
assert_eq!(acc.get(), 2);