Initial data commit

Task/Extensible-prime-generator/Swift/extensible-prime-generator.swift

@@ -0,0 +1,55 @@
+import Foundation
+
+func soeDictOdds() -> UnfoldSequence<Int, Int> {
+  var bp = 5; var q = 25
+  var bps: UnfoldSequence<Int, Int>.Iterator? = nil
+  var dict = [9: 6] // Dictionary<Int, Int>(9 => 6)
+  return sequence(state: 2, next: { n in
+    if n < 9 { if n < 3 { n = 3; return 2 }; defer {n += 2}; return n }
+    while n >= q || dict[n] != nil {
+      if n >= q {
+        let inc = bp + bp
+        dict[n + inc] = inc
+        if bps == nil {
+          bps = soeDictOdds().makeIterator()
+          bp = (bps?.next())!; bp = (bps?.next())!; bp = (bps?.next())! // skip 2/3/5...
+        }
+        bp = (bps?.next())!; q = bp * bp // guaranteed never nil
+      } else {
+        let inc = dict[n] ?? 0
+        dict[n] = nil
+        var next = n + inc
+        while dict[next] != nil { next += inc }
+        dict[next] = inc
+      }
+      n += 2
+    }
+    defer { n += 2 }; return n
+  })
+}
+
+print("The first 20 primes are:  ", terminator: "")
+soeDictOdds().lazy.prefix(20).forEach { print($0, "", terminator: "") }
+print()
+
+print("The primes between 100 and 150 are:  ", terminator: "")
+soeDictOdds().lazy.drop(while: { $0 < Prime(100) }).lazy.prefix(while: { $0 <= 150 })
+    .forEach { print($0, "", terminator: "") }
+print()
+
+print("The number of primes from 7700 to 8000 is  :", terminator: "")
+print(soeDictOdds().lazy.drop(while: { $0 < 7700 }).lazy.prefix(while: { $0 <= 8000 })
+        .lazy.reduce(0, { a, _ in a + 1 }))
+
+print("The 10,000th prime is:  ", terminator: "")
+print((soeDictOdds().lazy.dropFirst(9999).first { $0 == $0 })!)
+
+print("The sum of primes to 2 million is:  ", terminator: "")
+
+let start = NSDate()
+let answr = soeDictOdds().lazy.prefix(while: { $0 <= 2000000 })
+              .reduce(0, { a, p in a + Int64(p) })
+let elpsd = -start.timeIntervalSinceNow
+
+print(answr)
+print(String(format: "This test took %.3f milliseconds.", elpsd * 1000))