restore simple bits functions. Useful for setting/testing boolean values

inr MP transport, and for setting/clearing modifier bits in js config files.

Nasal/bits.nas

@@ -0,0 +1,37 @@
+var _bits = [var _ = 1];
+for (var i = 1; i < 32; i += 1)
+	append(_bits, _ += _);
+
+
+# returns number <n> as bit string: bits.string(6) -> "110"
+#
+var string = func(n) {
+	if (!n)
+		return '0';
+	var s = "";
+	while (n) {
+		s = ((var v = int(n / 2)) + v != n) ~ s;
+		n = v;
+	}
+	return s;
+}
+
+# checks whether bit <b> is set in number <n>
+#
+var test = func(n, b) {
+	while (b) {
+		n /= 2;
+		b -= 1;
+	}
+	int(n) != int(n / 2) * 2;
+}
+
+
+# returns number <n> with bit <b> set
+#
+var set = func(n, b) test(n, b) ? n : n + _bits[b];
+
+
+# returns number <n> with bit <b> cleared
+#
+var clear = func(n, b) test(n, b) ? n - _bits[b] : n;