schrodinger.kernel.Dirichlet.scala Maven / Gradle / Ivy
/*
* Copyright 2021 Arman Bilge
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package schrodinger.kernel
import algebra.ring.Semifield
import cats.Apply
import cats.NonEmptyTraverse
import cats.syntax.all.*
import schrodinger.math.syntax.*
trait Dirichlet[F[_], V]:
def dirichlet(concentration: V): F[V]
object Dirichlet:
inline def apply[F[_], V](concentration: V)(using d: Dirichlet[F, V]): F[V] =
d.dirichlet(concentration)
given [F[_]: Apply, G[_]: NonEmptyTraverse, A](using
A: Semifield[A],
g: Gamma[F, A],
): Dirichlet[F, G[A]] with
def dirichlet(concentration: G[A]) =
concentration.nonEmptyTraverse(Gamma(_, A.one)).map { xs =>
val sum = A.sum(xs.toIterable)
xs.map(_ / sum)
}