HistogramExample.scala

package ilc
package examples

import feature._

class HistogramExample
extends Example
   with MapReduce
   with integers.SyntaxSugar
   with integers.AbelianDerivation
   with integers.ToScala
{
  // userMap : ℤ → Bag ℤ → Bag (ℤ × ℤ)
  // userMap = λ ignoredDocumentID : ℤ.
  //   foldGroup freeAbelianGroup
  //     (λ number : ℤ. singleton (pair number 1))
  val userMap: UntypedTerm = 'ignoredDocumentId ->: FoldGroup(FreeAbelianGroup,
    'number ->: Singleton(Pair('number, LiteralInt(1))))

  // userReduce : ℤ → Bag ℤ → ℤ
  // userReduce = λ ignoredKey : ℤ.
  //   foldGroup additiveGroupOnIntegers (λx : ℤ. x)
  val userReduce = 'ignoredKey ->: FoldGroup(additiveGroupOnIntegers, 'x ->: 'x)

  // program : Map ℤ (Bag ℤ) → Map ℤ ℤ
  // program =
  //   mapReduce
  //     freeAbelianGroup
  //     additiveGroupOnIntegers
  //     userMap
  //     userReduce
  val untypedProgram: UntypedTerm =
    mapReduce(
      FreeAbelianGroup,
      additiveGroupOnIntegers,
      userMap,
      userReduce) ofType MapType(ℤ, BagType(ℤ)) =>: MapType(ℤ, ℤ)

  val program: Term = untypedTermToTerm(untypedProgram)
}