diff --git a/src/lib.rs b/src/lib.rs
index 1057a92..e7df38b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -202,17 +202,15 @@ impl<M: Material + Clone> Cell<M> {
         // Discretize (2): (\delta E_y)/(\delta t) = c^2 (-\delta B_z / \delta x - S_y)
         // Rearrange: \delta E_y = c (-\delta B_z / 2 - c \delta_t S_y)
         
-        use consts::real::{C, MU0};
+        use consts::real::{C, HALF, MU0};
 
-        let half = R64::from_inner(0.5);
-        
         let delta_bz_y = self.bz - up.bz;
         let static_ex: R64 = MU0() * self.mat.conductivity() * self.ex;
-        let delta_ex: R64 = C() * (half * delta_bz_y - C() * delta_t * static_ex);
+        let delta_ex: R64 = C() * (HALF() * delta_bz_y - C() * delta_t * static_ex);
 
         let delta_bz_x = self.bz - left.bz;
         let static_ey: R64 = MU0() * self.mat.conductivity() * self.ey;
-        let delta_ey: R64 = C() * (-half * delta_bz_x - C() * delta_t * static_ey);
+        let delta_ey: R64 = C() * (-HALF() * delta_bz_x - C() * delta_t * static_ey);
         
         Cell {
             ex: self.ex + delta_ex,