Initial data commit

Task/Subtractive-generator/D/subtractive-generator.d

@@ -0,0 +1,52 @@
+import std.stdio;
+
+struct Subtractive {
+    enum MOD = 1_000_000_000;
+    private int[55] state;
+    private int si, sj;
+
+    this(in int p1) pure nothrow {
+        subrandSeed(p1);
+    }
+
+    void subrandSeed(int p1) pure nothrow {
+        int p2 = 1;
+
+        state[0] = p1 % MOD;
+        for (int i = 1, j = 21; i < 55; i++, j += 21) {
+            if (j >= 55)
+                j -= 55;
+            state[j] = p2;
+            if ((p2 = p1 - p2) < 0)
+                p2 += MOD;
+            p1 = state[j];
+        }
+
+        si = 0;
+        sj = 24;
+        foreach (i; 0 .. 165)
+            subrand();
+    }
+
+    int subrand() pure nothrow {
+        if (si == sj)
+            subrandSeed(0);
+
+        if (!si--)
+            si = 54;
+        if (!sj--)
+            sj = 54;
+
+        int x = state[si] - state[sj];
+        if (x < 0)
+            x += MOD;
+
+        return state[si] = x;
+    }
+}
+
+void main() {
+    auto gen = Subtractive(292_929);
+    foreach (i; 0 .. 10)
+        writeln(gen.subrand());
+}