Spruce up formatting and error messages

Make the new code's formatting and error messages more consistent with
the previous code. I don't necessarily have a strong preference for the
previous conventions, but I do like stuff to be consistent.

app-proto/src/assembly.rs

@@ -308,10 +308,11 @@ impl Element for Point {
     
     fn default_regulators(self: Rc<Self>) -> Vec<Rc<dyn Regulator>> {
         all::<Axis>()
-            .map(|axis| {
+            .map(
-                Rc::new(PointCoordinateRegulator::new(self.clone(), axis))
+                |axis| Rc::new(
-                    as Rc::<dyn Regulator>
+                    PointCoordinateRegulator::new(self.clone(), axis)
-            })
+                ) as Rc::<dyn Regulator>
+            )
             .collect()
     }
     
@@ -538,19 +539,32 @@ impl PointCoordinateRegulator {
         let measurement = subject.representation().map(
             move |rep| rep[axis as usize]
         );
+        
         let set_point = create_signal(SpecifiedValue::from_empty_spec());
-        Self { subject, axis, measurement, set_point, serial: Self::next_serial() }
+        let serial = Self::next_serial();
+        
+        Self { subject, axis, measurement, set_point, serial }
     }
 }
 
 impl Serial for PointCoordinateRegulator {
-    fn serial(&self) -> u64 { self.serial }
+    fn serial(&self) -> u64 {
+        self.serial
+    }
 }
 
 impl Regulator for PointCoordinateRegulator {
-    fn subjects(&self) -> Vec<Rc<dyn Element>> { vec![self.subject.clone()] }
+    fn subjects(&self) -> Vec<Rc<dyn Element>> {
-    fn measurement(&self) -> ReadSignal<f64> { self.measurement }
+        vec![self.subject.clone()]
-    fn set_point(&self) -> Signal<SpecifiedValue> { self.set_point }
+    }
+    
+    fn measurement(&self) -> ReadSignal<f64> {
+        self.measurement
+    }
+    
+    fn set_point(&self) -> Signal<SpecifiedValue> {
+        self.set_point
+    }
 }
 
 impl ProblemPoser for PointCoordinateRegulator {
@@ -558,22 +572,25 @@ impl ProblemPoser for PointCoordinateRegulator {
         self.set_point.with_untracked(|set_pt| {
             if let Some(val) = set_pt.value {
                 let col = self.subject.column_index().expect(
-                    "Subject must be indexed before point-coordinate regulator poses.");
+                    "Subject should be indexed before point coordinate regulator writes problem data"
+                );
                 problem.frozen.push(self.axis as usize, col, val);
-                // Check if all three spatial coordinates have been frozen, and if so,
+                
-                // freeze the norm component as well
+                // if all three of the subject's spatial coordinates have been
-                let mut coords = [0.0; Axis::CARDINALITY];
+                // frozen, then freeze its norm component too
-                let mut nset: usize = 0;
+                let mut coords_frozen = [0.0; Axis::CARDINALITY];
+                let mut n_set: usize = 0;
                 for &MatrixEntry { index, value } in &(problem.frozen) {
-                    if index.1 == col && index.0 < Axis::CARDINALITY {
+                    let (row_frozen, col_frozen) = index;
-                        nset += 1;
+                    if col_frozen == col && row_frozen < Axis::CARDINALITY {
-                        coords[index.0] = value
+                        n_set += 1;
+                        coords_frozen[row_frozen] = value
                     }
                 }
-                if nset == Axis::CARDINALITY {
+                if n_set == Axis::CARDINALITY {
-                    let [x, y, z] = coords;
+                    let [x, y, z] = coords_frozen;
-                    problem.frozen.push(
+                    let norm = point(x, y, z)[Point::NORM_COMPONENT];
-                        Point::NORM_COMPONENT, col, point(x,y,z)[Point::NORM_COMPONENT]);
+                    problem.frozen.push(Point::NORM_COMPONENT, col, norm);
                 }
             }
         });