Fix tanya.math module name

source/tanya/math/package.d

@@ -0,0 +1,110 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Copyright: Eugene Wissner 2016.
+ * License: $(LINK2 https://www.mozilla.org/en-US/MPL/2.0/,
+ *                  Mozilla Public License, v. 2.0).
+ * Authors: $(LINK2 mailto:belka@caraus.de, Eugene Wissner)
+ */  
+module tanya.math;
+
+version (unittest)
+{
+	import std.algorithm.iteration;
+}
+
+/**
+ * Computes $(D_PARAM x) to the power $(D_PARAM y) modulo $(D_PARAM z).
+ *
+ * Params:
+ * 	x = Base.
+ * 	y = Exponent.
+ * 	z = Divisor.
+ *
+ * Returns: Reminder of the division of $(D_PARAM x) to the power $(D_PARAM y)
+ *          by $(D_PARAM z).
+ */
+ulong pow(ulong x, ulong y, ulong z) nothrow pure @safe @nogc
+in
+{
+	assert(z > 0);
+}
+out (result)
+{
+	assert(result >= 0);
+}
+body
+{
+    ulong mask = ulong.max / 2 + 1, result;
+
+	if (y == 0)
+	{
+		return 1 % z;
+	}
+	else if (y == 1)
+	{
+		return x % z;
+	}
+    do
+    {
+        auto bit = y & mask;
+        if (!result && bit)
+        {
+            result = x;
+            continue;
+        }
+
+        result *= result;
+        if (bit)
+        {
+            result *= x;
+        }
+        result %= z;
+
+    }
+    while (mask >>= 1);
+
+	return result;
+}
+
+///
+unittest
+{
+    assert(pow(3, 5, 7) == 5);
+    assert(pow(2, 2, 1) == 0);
+    assert(pow(3, 3, 3) == 0);
+    assert(pow(7, 4, 2) == 1);
+    assert(pow(53, 0, 2) == 1);
+    assert(pow(53, 1, 3) == 2);
+    assert(pow(53, 2, 5) == 4);
+    assert(pow(0, 0, 5) == 1);
+    assert(pow(0, 5, 5) == 0);
+}
+
+/**
+ * Checks if $(D_PARAM x) is a prime.
+ *
+ * Params:
+ * 	x = The number should be checked.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM x) is a prime number,
+ *          $(D_KEYWORD false) otherwise.
+ */
+bool isPseudoprime(ulong x) nothrow pure @safe @nogc
+{
+	return pow(2, x - 1, x) == 1;
+}
+
+///
+unittest
+{
+	uint[30] known = [74623, 74653, 74687, 74699, 74707, 74713, 74717, 74719,
+                      74843, 74747, 74759, 74761, 74771, 74779, 74797, 74821,
+	                  74827, 9973, 104729, 15485867, 49979693, 104395303,
+	                  593441861, 104729, 15485867, 49979693, 104395303,
+	                  593441861, 899809363, 982451653];
+
+	known.each!((ref x) => assert(isPseudoprime(x)));
+}