1 files changed, 66 insertions, 0 deletions
diff --git a/src/libnr/nr-rotate.h b/src/libnr/nr-rotate.h
new file mode 100644
index 000000000..051372ce6
--- /dev/null
+++ b/src/libnr/nr-rotate.h
@@ -0,0 +1,66 @@
+#ifndef SEEN_NR_ROTATE_H
+#define SEEN_NR_ROTATE_H
+
+/** \file
+ * Rotation about the origin.
+ */
+
+#include <libnr/nr-point.h>
+#include <libnr/nr-point-fns.h>
+#include <libnr/nr-point-ops.h>
+
+namespace NR {
+
+/** Notionally an NR::Matrix corresponding to rotation about the origin.
+    Behaves like NR::Matrix for multiplication.
+**/
+class rotate {
+public:
+    Point vec;
+
+private:
+    rotate();
+
+public:
+    explicit rotate(Coord theta);
+    explicit rotate(Point const &p) : vec(p) {}
+    explicit rotate(Coord const x, Coord const y) : vec(x, y) {}
+
+    bool operator==(rotate const &o) const {
+        return vec == o.vec;
+    }
+
+    bool operator!=(rotate const &o) const {
+        return vec != o.vec;
+    }
+
+    inline rotate &operator*=(rotate const &b);
+    /* Defined in nr-rotate-ops.h. */
+
+    rotate inverse() const {
+        /** \todo
+         * In the usual case that vec is a unit vector (within rounding error),
+         * dividing by len_sq is either a noop or numerically harmful. 
+         * Make a unit_rotate class (or the like) that knows its length is 1.
+         */
+        double const len_sq = dot(vec, vec);
+        return rotate( Point(vec[X], -vec[Y])
+                       / len_sq );
+    }
+};
+
+} /* namespace NR */
+
+
+#endif /* !SEEN_NR_ROTATE_H */
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :