sieve

jschannel/sieve.js

@@ -0,0 +1,84 @@
+// simplitic implementation of channel
+var Channel = function() {
+    var saved_value = null;
+    var saved_receiver = null;
+    var saved_sender = null;
+    var try_push = function() {
+        if (saved_value && saved_receiver) {
+            var r = saved_receiver;
+            var v = saved_value;
+            var s = saved_sender;
+            saved_value = saved_receiver = saved_sender = null;
+            r(v);
+            s();
+        }
+    };
+    return {
+        recv: function(recv_callback) {
+            if (saved_receiver) {
+                console.log("warn: more than on receiver?");
+            }
+            saved_receiver = recv_callback;
+            try_push();
+        },
+        send: function(value, send_callback) {
+            if (saved_value) {
+                console.log("warn: more than one send?");
+            }
+            saved_value = value;
+            saved_sender = send_callback;
+            try_push();
+        }
+    }
+};
+
+
+// And the sieve code:
+var counter = function(c) {
+    var i = 2;
+    var inc = function() {
+        i = i + 1;
+        return c.send(i, inc);
+    };
+    return c.send(i, inc);
+};
+
+var filter = function(prime, recv, send) {
+    var r = function(i) {
+        if (i % prime) {
+            return send.send(i, function() {
+                return recv.recv(r);
+            });
+        } else {
+            return recv.recv(r);
+        }
+    };
+    return recv.recv(r)
+}
+
+var sieve = function(primes) {
+    var count = Channel();
+    counter(count);
+
+    var new_prime = function(prime) {
+        primes.send(prime, function() {
+            var newc = Channel();
+            filter(prime, count, newc);
+            count = newc;
+            return count.recv(new_prime);
+        });
+    }
+    return count.recv(new_prime);
+};
+
+var primes = Channel();
+sieve(primes);
+
+var i = 10;
+var f = function(prime) {
+    console.log(prime);
+    i -= 1;
+    if (i)
+        primes.recv(f);
+};
+primes.recv(f);