Initial data commit

Task/Extensible-prime-generator/Dart/extensible-prime-generator.dart

@@ -0,0 +1,50 @@
+Iterable<int> primesMap() {
+    Iterable<int> oddprms() sync* {
+      yield(3); yield(5); // need at least 2 for initialization
+      final Map<int, int> bpmap = {9: 6};
+      final Iterator<int> bps = oddprms().iterator;
+      bps.moveNext(); bps.moveNext(); // skip past 3 to 5
+      int bp = bps.current;
+      int n = bp;
+      int q = bp * bp;
+      while (true) {
+        n += 2;
+        while (n >= q || bpmap.containsKey(n)) {
+          if (n >= q) {
+            final int inc = bp << 1;
+            bpmap[bp * bp + inc] = inc;
+            bps.moveNext(); bp = bps.current; q = bp * bp;
+          } else {
+            final int inc = bpmap.remove(n);
+            int next = n + inc;
+            while (bpmap.containsKey(next)) {
+              next += inc;
+            }
+            bpmap[next] = inc;
+          }
+          n += 2;
+        }
+        yield(n);
+      }
+    }
+    return [2].followedBy(oddprms());
+}
+
+void main() {
+  print("The first 20 primes:");
+  String str = "( ";
+  primesMap().take(20).forEach((p)=>str += "$p "); print(str + ")");
+  print("Primes between 100 and 150:");
+  str = "( ";
+  primesMap().skipWhile((p)=>p<100).takeWhile((p)=>p<150)
+    .forEach((p)=>str += "$p "); print(str + ")");
+  print("Number of primes between 7700 and 8000: ${
+    primesMap().skipWhile((p)=>p<7700).takeWhile((p)=>p<8000).length
+  }");
+  print("The 10,000th prime:  ${
+    primesMap().skip(9999).first
+  }");
+  final start = DateTime.now().millisecondsSinceEpoch;
+  final answer = primesMap().takeWhile((p)=>p<2000000).reduce((a,p)=>a+p);
+  final elapsed = DateTime.now().millisecondsSinceEpoch - start;
+}