zrx_stream/stream/operator/

count.rs

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// ----------------------------------------------------------------------------

//! Count operator.

use zrx_scheduler::{Id, Value};

use crate::stream::value::Collection;
use crate::stream::Stream;

// ----------------------------------------------------------------------------
// Implementations
// ----------------------------------------------------------------------------

impl<I, T> Stream<I, T>
where
    I: Id,
    T: Value + Clone + Eq,
{
    pub fn count(&self, id: I) -> Stream<I, usize> {
        self.reduce(id, |store: &dyn Collection<I, T>| {
            (!store.is_empty()).then_some(store.len())
        })
    }
}