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solution2.5.2.4.scala provided #72

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32 changes: 32 additions & 0 deletions chapter02/worksheets/solution2.5.2.4.scala
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/**
Exercise 2.5.2.4

For a, b, c of type Set[Int],
compute the set of all sets of the form Set(x, y, z)
where x is from a, y from b, and z from c.

The required type signature and a sample test:

def prod3(a: Set[Int], b: Set[Int], c: Set[Int]): Set[Set[Int]] = ???

scala> prod3(Set(1, 2), Set(3), Set(4, 5))
res0: Set[Set[Int]] = Set(Set(1,3,4), Set(1,3,5), Set(2,3,4), Set(2,3,5))

Hint: use flatMap.
*/

def prod3(a: Set[Int], b: Set[Int], c: Set[Int]): Set[Set[Int]] = {
val d = List(a, b, c)
d(0).flatMap{ x => d(1).flatMap{ y => d(2).map{ z => Set(x, y, z) }}}
}

val result = prod3(Set(1, 2), Set(3), Set(4, 5))
val expected: Set[Set[Int]] = Set(Set(1,3,4), Set(1,3,5), Set(2,3,4), Set(2,3,5))
assert(result == expected)

// scala> :load solution2.5.2.4.scala
// :load solution2.5.2.4.scala
// def prod3(a: Set[Int], b: Set[Int], c: Set[Int]): Set[Set[Int]]
// val result: Set[Set[Int]] = Set(Set(1, 3, 4), Set(1, 3, 5), Set(2, 3, 4), Set(2, 3, 5))
// val expected: Set[Set[Int]] = Set(Set(1, 3, 4), Set(1, 3, 5), Set(2, 3, 4), Set(2, 3, 5))

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