From 83ac0cda7bda56f46cbe31b7f0bc81c0eba61de3 Mon Sep 17 00:00:00 2001 From: Andreas Roehler Date: Tue, 29 Oct 2024 10:02:18 +0100 Subject: [PATCH] solution2.5.2.4.scala provided Signed-off-by: Andreas Roehler --- chapter02/worksheets/solution2.5.2.4.scala | 32 ++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 chapter02/worksheets/solution2.5.2.4.scala diff --git a/chapter02/worksheets/solution2.5.2.4.scala b/chapter02/worksheets/solution2.5.2.4.scala new file mode 100644 index 0000000..c6b4b01 --- /dev/null +++ b/chapter02/worksheets/solution2.5.2.4.scala @@ -0,0 +1,32 @@ +/** + 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)) +