fs2.data.pfsa.PDFA.scala Maven / Gradle / Ivy
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/*
* Copyright 2024 fs2-data Project
*
* 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 fs2.data.pfsa
import cats.Foldable
import cats.syntax.foldable._
import Pred.syntax._
private[data] class PDFA[P, T](val init: Int,
val finals: Set[Int],
val trap: Option[Int],
val transitions: Array[List[(P, Int)]])(implicit P: Pred[P, T]) {
def step(q: Int, t: T): Option[Int] =
if (q >= transitions.length)
None
else
transitions(q).collectFirst { case (p, q) if p.satisfies(t) => q }
def recognizes[S[_]: Foldable](input: S[T]): Boolean =
input
.foldLeftM((init, 0)) { case ((q, idx), c) =>
transitions
.lift(q)
.flatMap(_.collectFirst {
case (p, q) if p.satisfies(c) =>
(q, idx + 1)
})
}
.exists { case (q, idx) =>
idx == input.size && finals.contains(q)
}
}