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Task/Vector-products/D/vector-products.d

@@ -0,0 +1,44 @@
+import std.stdio, std.conv, std.numeric;
+
+struct V3 {
+    union {
+        immutable static struct { double x, y, z; }
+        immutable double[3] v;
+    }
+
+    double dot(in V3 rhs) /*@safe*/ const pure nothrow {
+        return dotProduct(v, rhs.v);
+    }
+
+    V3 cross(in V3 rhs) @safe const pure nothrow {
+        return V3(y * rhs.z - z * rhs.y,
+                  z * rhs.x - x * rhs.z,
+                  x * rhs.y - y * rhs.x);
+    }
+
+    string toString() /*@safe*/ const { return text(v); }
+}
+
+double scalarTriple(in V3 a, in V3 b, in V3 c)
+/*@safe*/ pure nothrow {
+    return a.dot(b.cross(c));
+    // function vector_products.V3.cross (const(V3) rhs) immutable
+    // is not callable using argument types (const(V3)) const
+}
+
+V3 vectorTriple(in V3 a, in V3 b, in V3 c) @safe pure nothrow {
+    return a.cross(b.cross(c));
+}
+
+void main() {
+    immutable V3 a = {3, 4, 5},
+                 b = {4, 3, 5},
+                 c = {-5, -12, -13};
+    writeln("a = ", a);
+    writeln("b = ", b);
+    writeln("c = ", c);
+    writeln("a . b = ", a.dot(b));
+    writeln("a x b = ", a.cross(b));
+    writeln("a . (b x c) = ", scalarTriple(a, b, c));
+    writeln("a x (b x c) = ", vectorTriple(a, b, c));
+}