add b and counter-clockwise rotation

src/main.rs

@@ -144,7 +144,51 @@ impl Cube {
         self.r.apply_l(u_bl, u_bm, u_br);
     }
 
-    // TODO: B
+    fn b(&mut self) {
+        self.b.rotate();
+        let (u_tl, u_tm, u_tr) = (self.u.tl, self.u.tm, self.u.tr);
+        self.u.apply_t(self.r.tr, self.r.mr, self.r.br);
+        self.r.apply_r(self.d.br, self.d.bm, self.d.bl);
+        self.d.apply_b(self.l.tl, self.l.ml, self.l.bl);
+        self.l.apply_l(u_tr, u_tm, u_tl);
+    }
+
+    // TODO: efficient counter-clockwise
+    fn up(&mut self) {
+        self.u();
+        self.u();
+        self.u();
+    }
+
+    fn dp(&mut self) {
+        self.d();
+        self.d();
+        self.d();
+    }
+
+    fn lp(&mut self) {
+        self.l();
+        self.l();
+        self.l();
+    }
+
+    fn rp(&mut self) {
+        self.r();
+        self.r();
+        self.r();
+    }
+
+    fn fp(&mut self) {
+        self.f();
+        self.f();
+        self.f();
+    }
+
+    fn bp(&mut self) {
+        self.b();
+        self.b();
+        self.b();
+    }
 }
 
 fn main() {
@@ -214,4 +258,16 @@ mod tests {
         assert_eq!(c.r.tl, Color::Y);
         assert_eq!(c.b, Face::new(Color::B));
     }
+
+    #[test]
+    fn test_b() {
+        let mut c = Cube::new();
+        c.b();
+        assert_eq!(c.b, Face::new(Color::B));
+        assert_eq!(c.u.tl, Color::O);
+        assert_eq!(c.l.bl, Color::Y);
+        assert_eq!(c.d.br, Color::R);
+        assert_eq!(c.r.tr, Color::W);
+        assert_eq!(c.f, Face::new(Color::G));
+    }
 }