365
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
1 |
def concat(A: Set[String], B: Set[String]) : Set[String] =
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
2 |
for (x <-A ; y <- B) yield x ++ y
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
3 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
4 |
def pow(A: Set[String], n: Int) : Set[String] = n match {
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
5 |
case 0 => Set("")
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
6 |
case n => concat(A, pow(A, n- 1))
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
7 |
}
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
8 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
9 |
val A = Set("a", "b", "c", "d")
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
10 |
pow(A, 4).size // -> 256
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
11 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
12 |
val B = Set("a", "b", "c", "")
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
13 |
pow(B, 4).size // -> 121
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
14 |
|
471
|
15 |
|
|
16 |
|
397
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
17 |
val B2 = Set("a", "b", "c", "")
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
18 |
pow(B2, 3).size // -> 40
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
diff
changeset
|
19 |
|
365
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
20 |
val C = Set("a", "b", "")
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
21 |
pow(C, 2)
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
22 |
pow(C, 2).size // -> 7
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
23 |
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
24 |
pow(C, 3)
|
Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
diff
changeset
|
25 |
pow(C, 3).size // -> 15
|