diff --git a/src/lib.rs b/src/lib.rs
index 0a0c9c8..339bb5c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,6 +3,7 @@ use wasm_bindgen::prelude::*;
 mod maxwell;
 mod operators;
 use maxwell::{System, WorkBuffers};
+use operators::Upwind4;
 
 #[cfg(feature = "wee_alloc")]
 #[global_allocator]
@@ -34,7 +35,7 @@ impl Universe {
     }
 
     pub fn advance(&mut self, dt: f32) {
-        self.sys.0.advance(&mut self.sys.1, dt, Some(&mut self.wb));
+        System::advance::<Upwind4>(&self.sys.0, &mut self.sys.1, dt, Some(&mut self.wb));
         std::mem::swap(&mut self.sys.0, &mut self.sys.1);
     }
 
diff --git a/src/maxwell.rs b/src/maxwell.rs
index 2f87226..89ed152 100644
--- a/src/maxwell.rs
+++ b/src/maxwell.rs
@@ -1,4 +1,4 @@
-use super::operators::{diffx, diffy};
+use super::operators::SbpOperator;
 use ndarray::{Array2, Zip};
 
 pub struct System {
@@ -43,7 +43,10 @@ impl System {
         }
     }
 
-    pub fn advance(&self, fut: &mut System, dt: f32, work_buffers: Option<&mut WorkBuffers>) {
+    pub fn advance<SBP>(&self, fut: &mut System, dt: f32, work_buffers: Option<&mut WorkBuffers>)
+    where
+        SBP: SbpOperator,
+    {
         assert_eq!(self.ex.shape(), fut.ex.shape());
 
         let mut wb: WorkBuffers;
@@ -84,18 +87,18 @@ impl System {
 
             // ex = hz_y
             k[i].0.fill(0.0);
-            diffy(y.1.view(), k[i].0.view_mut());
+            SBP::diffy(y.1.view(), k[i].0.view_mut());
 
             // ey = -hz_x
             k[i].2.fill(0.0);
-            diffx(y.1.view(), k[i].2.view_mut());
+            SBP::diffx(y.1.view(), k[i].2.view_mut());
             k[i].2.mapv_inplace(|v| -v);
 
             // hz = -ey_x + ex_y
             k[i].1.fill(0.0);
-            diffx(y.2.view(), k[i].1.view_mut());
+            SBP::diffx(y.2.view(), k[i].1.view_mut());
             k[i].1.mapv_inplace(|v| -v);
-            diffy(y.0.view(), k[i].1.view_mut());
+            SBP::diffy(y.0.view(), k[i].1.view_mut());
 
             // Boundary conditions (SAT)
             let ny = y.0.shape()[0];
diff --git a/src/operators.rs b/src/operators.rs
index 3f9109d..9fd66c4 100644
--- a/src/operators.rs
+++ b/src/operators.rs
@@ -1,344 +1,10 @@
-#![allow(dead_code)]
-use ndarray::{arr1, arr2, s, ArrayView1, ArrayView2, ArrayViewMut1, ArrayViewMut2};
+use ndarray::{ArrayView2, ArrayViewMut2};
 
-pub(crate) fn diffx(prev: ArrayView2<f32>, mut fut: ArrayViewMut2<f32>) {
-    for j in 0..prev.shape()[0] {
-        upwind4(prev.slice(s!(j, ..)), fut.slice_mut(s!(j, ..)));
-    }
+pub trait SbpOperator {
+    fn diffx(prev: ArrayView2<f32>, fut: ArrayViewMut2<f32>);
+    fn diffy(prev: ArrayView2<f32>, fut: ArrayViewMut2<f32>);
+    fn h() -> &'static [f32];
 }
 
-pub(crate) fn diffx_periodic(prev: ArrayView2<f32>, mut fut: ArrayViewMut2<f32>) {
-    for j in 0..prev.shape()[0] {
-        upwind4_periodic(prev.slice(s!(j, ..)), fut.slice_mut(s!(j, ..)));
-    }
-}
-
-pub(crate) fn diffy(prev: ArrayView2<f32>, mut fut: ArrayViewMut2<f32>) {
-    for i in 0..prev.shape()[1] {
-        upwind4(prev.slice(s!(.., i)), fut.slice_mut(s!(.., i)));
-    }
-}
-
-pub(crate) fn diffy_periodic(prev: ArrayView2<f32>, mut fut: ArrayViewMut2<f32>) {
-    for i in 0..prev.shape()[1] {
-        upwind4_periodic(prev.slice(s!(.., i)), fut.slice_mut(s!(.., i)));
-    }
-}
-
-pub(crate) fn dissx(prev: ArrayView2<f32>, mut fut: ArrayViewMut2<f32>) {
-    for j in 0..prev.shape()[0] {
-        upwind4_diss(prev.slice(s!(j, ..)), fut.slice_mut(s!(j, ..)));
-    }
-}
-pub(crate) fn dissy(prev: ArrayView2<f32>, mut fut: ArrayViewMut2<f32>) {
-    for i in 0..prev.shape()[1] {
-        upwind4_diss(prev.slice(s!(.., i)), fut.slice_mut(s!(.., i)));
-    }
-}
-
-fn trad4_periodic(prev: ArrayView1<f32>, mut fut: ArrayViewMut1<f32>) {
-    assert_eq!(prev.shape(), fut.shape());
-    let nx = prev.shape()[0];
-
-    let dx = 1.0 / (nx - 1) as f32;
-
-    let diag = [1.0 / 12.0, -2.0 / 3.0, 0.0, 2.0 / 3.0, -1.0 / 12.0];
-
-    let diff = diag[0] * prev[(nx - 2)]
-        + diag[1] * prev[(nx - 1)]
-        + diag[2] * prev[(0)]
-        + diag[3] * prev[(1)]
-        + diag[4] * prev[(2)];
-    fut[(0)] += diff / dx;
-    let diff = diag[0] * prev[(nx - 1)]
-        + diag[1] * prev[(0)]
-        + diag[2] * prev[(1)]
-        + diag[3] * prev[(2)]
-        + diag[4] * prev[(3)];
-    fut[(1)] += diff / dx;
-    for i in 2..nx - 2 {
-        let diff = diag[0] * prev[(i - 2)]
-            + diag[1] * prev[(i - 1)]
-            + diag[2] * prev[(i)]
-            + diag[3] * prev[(i + 1)]
-            + diag[4] * prev[(i + 2)];
-        fut[(i)] += diff / dx;
-    }
-    let diff = diag[0] * prev[(nx - 4)]
-        + diag[1] * prev[(nx - 3)]
-        + diag[2] * prev[(nx - 2)]
-        + diag[3] * prev[(nx - 1)]
-        + diag[4] * prev[(0)];
-    fut[(nx - 2)] += diff / dx;
-    let diff = diag[0] * prev[(nx - 3)]
-        + diag[1] * prev[(nx - 2)]
-        + diag[2] * prev[(nx - 1)]
-        + diag[3] * prev[(0)]
-        + diag[4] * prev[(1)];
-    fut[(nx - 1)] += diff / dx;
-}
-
-fn upwind4(prev: ArrayView1<f32>, mut fut: ArrayViewMut1<f32>) {
-    assert_eq!(prev.shape(), fut.shape());
-    let nx = prev.shape()[0];
-
-    let dx = 1.0 / (nx - 1) as f32;
-
-    let diag = arr1(&[
-        -1.0 / 24.0,
-        1.0 / 4.0,
-        -7.0 / 8.0,
-        0.0,
-        7.0 / 8.0,
-        -1.0 / 4.0,
-        1.0 / 24.0,
-    ]);
-
-    let block = arr2(&[
-        [
-            -72.0 / 49.0f32,
-            187.0 / 98.0,
-            -20.0 / 49.0,
-            -3.0 / 98.0,
-            0.0,
-            0.0,
-            0.0,
-        ],
-        [
-            -187.0 / 366.0,
-            0.0,
-            69.0 / 122.0,
-            -16.0 / 183.0,
-            2.0 / 61.0,
-            0.0,
-            0.0,
-        ],
-        [
-            20.0 / 123.0,
-            -69.0 / 82.0,
-            0.0,
-            227.0 / 246.0,
-            -12.0 / 41.0,
-            2.0 / 41.0,
-            0.0,
-        ],
-        [
-            3.0 / 298.0,
-            16.0 / 149.0,
-            -227.0 / 298.0,
-            0.0,
-            126.0 / 149.0,
-            -36.0 / 149.0,
-            6.0 / 149.0,
-        ],
-    ]);
-
-    // let h_block = [49.0 / 144.0, 61.0 / 48.0, 41.0 / 48.0, 149.0 / 144.0];
-
-    let first_elems = prev.slice(s!(..7));
-    for i in 0..4 {
-        let diff = first_elems.dot(&block.slice(s!(i, ..)));
-        fut[i] += diff / dx;
-    }
-
-    for i in 4..nx - 4 {
-        let diff = diag.dot(&prev.slice(s!(i - 3..i + 3 + 1)));
-        fut[(i)] += diff / dx;
-    }
-    let last_elems = prev.slice(s!(nx - 7..));
-    for i in 0..4 {
-        let ii = nx - 4 + i;
-        let block = block.slice(s!(3 - i, ..;-1));
-        let diff = last_elems.dot(&block);
-        fut[ii] += -diff / dx;
-    }
-}
-
-fn upwind4_periodic(prev: ArrayView1<f32>, mut fut: ArrayViewMut1<f32>) {
-    assert_eq!(prev.shape(), fut.shape());
-    let nx = prev.shape()[0];
-
-    let dx = 1.0 / (nx - 1) as f32;
-
-    let diag = [
-        -1.0 / 24.0,
-        1.0 / 4.0,
-        -7.0 / 8.0,
-        0.0,
-        7.0 / 8.0,
-        -1.0 / 4.0,
-        1.0 / 24.0,
-    ];
-
-    let diff = diag[0] * prev[(nx - 3)]
-        + diag[1] * prev[(nx - 2)]
-        + diag[2] * prev[(nx - 1)]
-        + diag[3] * prev[(0)]
-        + diag[4] * prev[(1)]
-        + diag[5] * prev[(2)]
-        + diag[6] * prev[(3)];
-    fut[0] += diff / dx;
-    let diff = diag[0] * prev[(nx - 2)]
-        + diag[1] * prev[(nx - 1)]
-        + diag[2] * prev[(0)]
-        + diag[3] * prev[(1)]
-        + diag[4] * prev[(2)]
-        + diag[5] * prev[(3)]
-        + diag[6] * prev[(4)];
-    fut[1] += diff / dx;
-    let diff = diag[0] * prev[(nx - 1)]
-        + diag[1] * prev[(0)]
-        + diag[2] * prev[(1)]
-        + diag[3] * prev[(2)]
-        + diag[4] * prev[(3)]
-        + diag[5] * prev[(4)]
-        + diag[6] * prev[(5)];
-    fut[2] += diff / dx;
-
-    for i in 3..nx - 3 {
-        let diff = diag[0] * prev[(i - 3)]
-            + diag[1] * prev[(i - 2)]
-            + diag[2] * prev[(i - 1)]
-            + diag[3] * prev[(i)]
-            + diag[4] * prev[(i + 1)]
-            + diag[5] * prev[(i + 2)]
-            + diag[6] * prev[(i + 3)];
-        fut[(i)] += diff / dx;
-    }
-    let diff = diag[0] * prev[(nx - 6)]
-        + diag[1] * prev[(nx - 5)]
-        + diag[2] * prev[(nx - 4)]
-        + diag[3] * prev[(nx - 3)]
-        + diag[4] * prev[(nx - 2)]
-        + diag[5] * prev[(nx - 1)]
-        + diag[6] * prev[(0)];
-    fut[(nx - 3)] += diff / dx;
-    let diff = diag[0] * prev[(nx - 5)]
-        + diag[1] * prev[(nx - 4)]
-        + diag[2] * prev[(nx - 3)]
-        + diag[3] * prev[(nx - 2)]
-        + diag[4] * prev[(nx - 1)]
-        + diag[5] * prev[(0)]
-        + diag[6] * prev[(1)];
-    fut[(nx - 2)] += diff / dx;
-    let diff = diag[0] * prev[(nx - 4)]
-        + diag[1] * prev[(nx - 3)]
-        + diag[2] * prev[(nx - 2)]
-        + diag[3] * prev[(nx - 1)]
-        + diag[4] * prev[(0)]
-        + diag[5] * prev[(1)]
-        + diag[6] * prev[(2)];
-    fut[(nx - 1)] += diff / dx;
-}
-
-#[test]
-fn upwind4_test() {
-    let nx = 20;
-    let dx = 1.0 / (nx - 1) as f32;
-    let mut source: ndarray::Array1<f32> = ndarray::Array1::zeros((nx));
-    let mut res = ndarray::Array1::zeros((nx));
-    let mut target = ndarray::Array1::zeros((nx));
-
-    for i in 0..nx {
-        source[i] = i as f32 * dx;
-        target[i] = 1.0;
-    }
-    res.fill(0.0);
-    upwind4(source.view(), res.view_mut());
-    assert!(res.all_close(&target, 1e-4));
-
-    for i in 0..nx {
-        let x = i as f32 * dx;
-        source[i] = x * x;
-        target[i] = 2.0 * x;
-    }
-    res.fill(0.0);
-    upwind4(source.view(), res.view_mut());
-    assert!(res.all_close(&target, 1e-4));
-
-    for i in 0..nx {
-        let x = i as f32 * dx;
-        source[i] = x * x * x;
-        target[i] = 3.0 * x * x;
-    }
-    res.fill(0.0);
-    upwind4(source.view(), res.view_mut());
-    assert!(res.all_close(&target, 1e-2));
-}
-
-fn upwind4_diss(prev: ArrayView1<f32>, mut fut: ArrayViewMut1<f32>) {
-    assert_eq!(prev.shape(), fut.shape());
-    let nx = prev.shape()[0];
-
-    let dx = 1.0 / (nx - 1) as f32;
-
-    let diag = [
-        1.0 / 24.0,
-        -1.0 / 4.0,
-        5.0 / 8.0,
-        -5.0 / 6.0,
-        5.0 / 8.0,
-        -1.0 / 4.0,
-        1.0 / 24.0,
-    ];
-
-    let diff = diag[0] * prev[(nx - 3)]
-        + diag[1] * prev[(nx - 2)]
-        + diag[2] * prev[(nx - 1)]
-        + diag[3] * prev[(0)]
-        + diag[4] * prev[(1)]
-        + diag[5] * prev[(2)]
-        + diag[6] * prev[(3)];
-    fut[0] += diff / dx;
-    let diff = diag[0] * prev[(nx - 2)]
-        + diag[1] * prev[(nx - 1)]
-        + diag[2] * prev[(0)]
-        + diag[3] * prev[(1)]
-        + diag[4] * prev[(2)]
-        + diag[5] * prev[(3)]
-        + diag[6] * prev[(4)];
-    fut[1] += diff / dx;
-    let diff = diag[0] * prev[(nx - 1)]
-        + diag[1] * prev[(0)]
-        + diag[2] * prev[(1)]
-        + diag[3] * prev[(2)]
-        + diag[4] * prev[(3)]
-        + diag[5] * prev[(4)]
-        + diag[6] * prev[(5)];
-    fut[2] += diff / dx;
-
-    for i in 3..nx - 3 {
-        let diff = diag[0] * prev[(i - 3)]
-            + diag[1] * prev[(i - 2)]
-            + diag[2] * prev[(i - 1)]
-            + diag[3] * prev[(i)]
-            + diag[4] * prev[(i + 1)]
-            + diag[5] * prev[(i + 2)]
-            + diag[6] * prev[(i + 3)];
-        fut[(i)] += diff / dx;
-    }
-    let diff = diag[0] * prev[(nx - 6)]
-        + diag[1] * prev[(nx - 5)]
-        + diag[2] * prev[(nx - 4)]
-        + diag[3] * prev[(nx - 3)]
-        + diag[4] * prev[(nx - 2)]
-        + diag[5] * prev[(nx - 1)]
-        + diag[6] * prev[(0)];
-    fut[(nx - 3)] += diff / dx;
-    let diff = diag[0] * prev[(nx - 5)]
-        + diag[1] * prev[(nx - 4)]
-        + diag[2] * prev[(nx - 3)]
-        + diag[3] * prev[(nx - 2)]
-        + diag[4] * prev[(nx - 1)]
-        + diag[5] * prev[(0)]
-        + diag[6] * prev[(1)];
-    fut[(nx - 2)] += diff / dx;
-    let diff = diag[0] * prev[(nx - 4)]
-        + diag[1] * prev[(nx - 3)]
-        + diag[2] * prev[(nx - 2)]
-        + diag[3] * prev[(nx - 1)]
-        + diag[4] * prev[(0)]
-        + diag[5] * prev[(1)]
-        + diag[6] * prev[(2)];
-    fut[(nx - 1)] += diff / dx;
-}
+mod upwind4;
+pub use upwind4::Upwind4;
diff --git a/src/operators/upwind4.rs b/src/operators/upwind4.rs
new file mode 100644
index 0000000..760ad3c
--- /dev/null
+++ b/src/operators/upwind4.rs
@@ -0,0 +1,136 @@
+use super::SbpOperator;
+use ndarray::{arr1, arr2, s, ArrayView1, ArrayView2, ArrayViewMut1, ArrayViewMut2};
+
+pub struct Upwind4 {}
+
+impl Upwind4 {
+    const HBLOCK: &'static [f32] = &[49.0 / 144.0, 61.0 / 48.0, 41.0 / 48.0, 149.0 / 144.0];
+    const DIAG: &'static [f32] = &[
+        -1.0 / 24.0,
+        1.0 / 4.0,
+        -7.0 / 8.0,
+        0.0,
+        7.0 / 8.0,
+        -1.0 / 4.0,
+        1.0 / 24.0,
+    ];
+    const BLOCK: &'static [[f32; 7]] = &[
+        [
+            -72.0 / 49.0f32,
+            187.0 / 98.0,
+            -20.0 / 49.0,
+            -3.0 / 98.0,
+            0.0,
+            0.0,
+            0.0,
+        ],
+        [
+            -187.0 / 366.0,
+            0.0,
+            69.0 / 122.0,
+            -16.0 / 183.0,
+            2.0 / 61.0,
+            0.0,
+            0.0,
+        ],
+        [
+            20.0 / 123.0,
+            -69.0 / 82.0,
+            0.0,
+            227.0 / 246.0,
+            -12.0 / 41.0,
+            2.0 / 41.0,
+            0.0,
+        ],
+        [
+            3.0 / 298.0,
+            16.0 / 149.0,
+            -227.0 / 298.0,
+            0.0,
+            126.0 / 149.0,
+            -36.0 / 149.0,
+            6.0 / 149.0,
+        ],
+    ];
+
+    fn diff(prev: ArrayView1<f32>, mut fut: ArrayViewMut1<f32>) {
+        assert_eq!(prev.shape(), fut.shape());
+        let nx = prev.shape()[0];
+
+        let dx = 1.0 / (nx - 1) as f32;
+
+        let diag = arr1(Upwind4::DIAG);
+        let block = arr2(Upwind4::BLOCK);
+
+        let first_elems = prev.slice(s!(..7));
+        for i in 0..4 {
+            let diff = first_elems.dot(&block.slice(s!(i, ..)));
+            fut[i] += diff / dx;
+        }
+
+        for i in 4..nx - 4 {
+            let diff = diag.dot(&prev.slice(s!(i - 3..i + 3 + 1)));
+            fut[(i)] += diff / dx;
+        }
+        let last_elems = prev.slice(s!(nx - 7..));
+        for i in 0..4 {
+            let ii = nx - 4 + i;
+            let block = block.slice(s!(3 - i, ..;-1));
+            let diff = last_elems.dot(&block);
+            fut[ii] += -diff / dx;
+        }
+    }
+}
+
+#[test]
+fn upwind4_test() {
+    let nx = 20;
+    let dx = 1.0 / (nx - 1) as f32;
+    let mut source: ndarray::Array1<f32> = ndarray::Array1::zeros(nx);
+    let mut res = ndarray::Array1::zeros(nx);
+    let mut target = ndarray::Array1::zeros(nx);
+
+    for i in 0..nx {
+        source[i] = i as f32 * dx;
+        target[i] = 1.0;
+    }
+    res.fill(0.0);
+    Upwind4::diff(source.view(), res.view_mut());
+    assert!(res.all_close(&target, 1e-4));
+
+    for i in 0..nx {
+        let x = i as f32 * dx;
+        source[i] = x * x;
+        target[i] = 2.0 * x;
+    }
+    res.fill(0.0);
+    Upwind4::diff(source.view(), res.view_mut());
+    assert!(res.all_close(&target, 1e-4));
+
+    for i in 0..nx {
+        let x = i as f32 * dx;
+        source[i] = x * x * x;
+        target[i] = 3.0 * x * x;
+    }
+    res.fill(0.0);
+    Upwind4::diff(source.view(), res.view_mut());
+    assert!(res.all_close(&target, 1e-2));
+}
+
+impl SbpOperator for Upwind4 {
+    fn diffx(prev: ArrayView2<f32>, mut fut: ArrayViewMut2<f32>) {
+        for j in 0..prev.shape()[0] {
+            Upwind4::diff(prev.slice(s!(j, ..)), fut.slice_mut(s!(j, ..)));
+        }
+    }
+
+    fn diffy(prev: ArrayView2<f32>, mut fut: ArrayViewMut2<f32>) {
+        for i in 0..prev.shape()[1] {
+            Upwind4::diff(prev.slice(s!(.., i)), fut.slice_mut(s!(.., i)));
+        }
+    }
+
+    fn h() -> &'static [f32] {
+        Upwind4::HBLOCK
+    }
+}