Move integrate to separate crate

multigrid/src/file.rs

@@ -38,7 +38,8 @@ impl OutputThread {
         match self.rx.as_ref().unwrap().try_recv() {
             Ok(mut copy_fields) => {
                 for (from, to) in fields.iter().zip(copy_fields.iter_mut()) {
-                    to.assign(&from);
+                    use integrate::Integrable;
+                    euler::Field::assign(to, from);
                 }
                 self.tx
                     .as_ref()

multigrid/src/main.rs

@@ -106,7 +106,7 @@ impl System {
             .iter_mut()
             .map(|k| k.as_mut_slice())
             .collect::<Vec<_>>();
-        sbp::integrate::integrate_multigrid::<sbp::integrate::Rk4, _, _, _>(
+        integrate::integrate_multigrid::<integrate::Rk4, euler::Field, _>(
             rhs,
             &self.fnow,
             &mut self.fnext,