pub interface IFindHandler<T>(data T) (res bool)

pub component Find<T>(data stream<T>) (res T, miss any)) {
  nodes { handler IFindHandler<T> }
  // ...
}

type Obj struct {
    id int
    name string
}

const objs list<Obj> = [
    { id: 1, name: "a" }
    { id: 2, name: "b" }
    { id: 3, name: "c" }
    { id: 42, name: "You found me!" }
    { id: 4, name: "d" }
]

component Main(start) (stop) {
    nodes {
        Find<Obj>{IsID42},
        Println
    }
    :start -> ($objs -> find)
    find:res -> println
    find:miss -> ("not found :(" -> println)
    println -> :stop
}

component IsID42(data Obj) (res bool) {
    nodes { Eq }
    :data.id -> eq:actual
    42 -> eq:expected
    eq -> :res
}