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

@@ -127,7 +127,7 @@ pub trait Element: Serial + ProblemPoser + DisplayItem {
 }
 
 impl Debug for dyn Element {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), fmt::Error> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         self.id().fmt(f)
     }
 }
@@ -305,13 +305,14 @@ impl Element for Point {
             point(0.0, 0.0, 0.0),
         )
     }
-
+    
     fn default_regulators(self: Rc<Self>) -> Vec<Rc<dyn Regulator>> {
         all::<Axis>()
-            .map(|axis| {
-                Rc::new(PointCoordinateRegulator::new(self.clone(), axis))
-                    as Rc::<dyn Regulator>
-            })
+            .map(
+                |axis| Rc::new(
+                    PointCoordinateRegulator::new(self.clone(), axis)
+                ) as Rc::<dyn Regulator>
+            )
             .collect()
     }
     
@@ -511,10 +512,18 @@ impl ProblemPoser for HalfCurvatureRegulator {
 }
 
 #[derive(Clone, Copy, Sequence)]
-pub enum Axis {X = 0, Y = 1, Z = 2}
+pub enum Axis { X = 0, Y = 1, Z = 2 }
 
 impl Axis {
-    pub const NAME: [&str; Axis::CARDINALITY] = ["X", "Y", "Z"];
+    fn name(&self) -> &'static str {
+        match self { Axis::X => "X", Axis::Y => "Y", Axis::Z => "Z" }
+    }
+}
+
+impl fmt::Display for Axis {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(self.name())
+    }
 }
 
 pub struct PointCoordinateRegulator {
@@ -530,19 +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 measurement(&self) -> ReadSignal<f64> { self.measurement }
-    fn set_point(&self) -> Signal<SpecifiedValue> { self.set_point }
+    fn subjects(&self) -> Vec<Rc<dyn Element>> {
+        vec![self.subject.clone()]
+    }
+    
+    fn measurement(&self) -> ReadSignal<f64> {
+        self.measurement
+    }
+    
+    fn set_point(&self) -> Signal<SpecifiedValue> {
+        self.set_point
+    }
 }
 
 impl ProblemPoser for PointCoordinateRegulator {
@@ -550,22 +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
-                let mut coords = [0.0; Axis::CARDINALITY];
-                let mut nset: usize = 0;
-                for &MatrixEntry {index, value} in &(problem.frozen) {
-                    if index.1 == col && index.0 < Axis::CARDINALITY {
-                        nset += 1;
-                        coords[index.0] = value
+                
+                // if all three of the subject's spatial coordinates have been
+                // frozen, then freeze its norm component too
+                let mut coords_frozen = [0.0; Axis::CARDINALITY];
+                let mut n_set: usize = 0;
+                for &MatrixEntry { index, value } in &(problem.frozen) {
+                    let (row_frozen, col_frozen) = index;
+                    if col_frozen == col && row_frozen < Axis::CARDINALITY {
+                        n_set += 1;
+                        coords_frozen[row_frozen] = value
                     }
                 }
-                if nset == Axis::CARDINALITY {
-                    let [x, y, z] = coords;
-                    problem.frozen.push(
-                        Point::NORM_COMPONENT, col, point(x,y,z)[Point::NORM_COMPONENT]);
+                if n_set == Axis::CARDINALITY {
+                    let [x, y, z] = coords_frozen;
+                    let norm = point(x, y, z)[Point::NORM_COMPONENT];
+                    problem.frozen.push(Point::NORM_COMPONENT, col, norm);
                 }
             }
         });

app-proto/src/components/outline.rs

@@ -6,7 +6,6 @@ use web_sys::{KeyboardEvent, MouseEvent, wasm_bindgen::JsCast};
 use crate::{
     AppState,
     assembly::{
-        Axis,
         Element,
         HalfCurvatureRegulator,
         InversiveDistanceRegulator,
@@ -123,7 +122,7 @@ impl OutlineItem for HalfCurvatureRegulator {
 
 impl OutlineItem for PointCoordinateRegulator {
     fn outline_item(self: Rc<Self>, _element: &Rc<dyn Element>) -> View {
-        let name = format!("{} coordinate", Axis::NAME[self.axis as usize]);
+        let name = format!("{} coordinate", self.axis);
         view! {
             li(class = "regulator") {
                 div(class = "regulator-label") // for spacing