tasks a-s

Task/Permutation-test/D/permutation-test.d

@@ -0,0 +1,32 @@
+import std.stdio, std.algorithm, std.array;
+// http://rosettacode.org/wiki/Combinations#D
+import combinations3: combinations;
+
+auto permTest(T)(T[] a, T[] b, in int precisionAdjust=100) {
+    alias reduce!q{a + b} sum; // statistic can be degenerate to sum
+
+    auto ab = a ~ b;
+    ab[] *= precisionAdjust; // scale up magnitude
+    auto tObs = sum(ab[0 .. a.length]);
+    auto comb = combinations!false(ab, a.length);
+
+    // combinations() isn't a Range yet
+    //immutable int under = comb.count!(c => stat(c) <= tObs)();
+    int under = 0;
+    foreach (c; comb)
+        if (sum(c) <= tObs)
+            under++;
+
+    return 1.0L * under / comb.length;
+}
+
+void main() {
+    auto treatment = [0.85, 0.88, 0.75, 0.66, 0.25, 0.29,
+                      0.83, 0.39, 0.97];
+    auto control = [0.68, 0.41, 0.10, 0.49, 0.16, 0.65,
+                    0.32, 0.92, 0.28, 0.98];
+
+    auto r = permTest(treatment, control);
+    writefln("under =%6.2f%%\nover  =%6.2f%%",
+             r * 100.0, (1 - r) * 100.0);
+}