org.emmalanguage.examples.graphs.EnumerateTriangles.scala Maven / Gradle / Ivy

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/*
 * Copyright © 2014 TU Berlin ([email protected])
 *
 * 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 org.emmalanguage
package examples.graphs

import api._
import model._

import scala.Ordering.Implicits._

@emma.lib
object EnumerateTriangles {

  def apply[V: Ordering: Meta.Tag](edges: DataBag[Edge[V]]): DataBag[Triangle[V]] = {
    // generate all triangles (x - v - w) such that x < v < w
    val triangles = for {
      Edge(x, u) <- edges
      Edge(y, v) <- edges
      Edge(z, w) <- edges
      if x < u
      if y < v
      if z < w
      if u == y
      if x == z
      if v == w
    } yield Triangle(x, u, v)
    // return
    triangles
  }
}