From aeace1a56291a1bf8316ce46acccc51db7f805eb Mon Sep 17 00:00:00 2001
From: Glen Whitney <glen@studioinfinity.org>
Date: Sun, 21 Sep 2025 22:30:38 -0700
Subject: [PATCH] refactor: macro to infer const array length

---
 .../src/components/test_assembly_chooser.rs   | 30 ++++++++++++-------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/app-proto/src/components/test_assembly_chooser.rs b/app-proto/src/components/test_assembly_chooser.rs
index 86ad836..1444325 100644
--- a/app-proto/src/components/test_assembly_chooser.rs
+++ b/app-proto/src/components/test_assembly_chooser.rs
@@ -19,6 +19,14 @@ use crate::{
     specified::SpecifiedValue,
 };
 
+// Convenience: macro to allow elision of const array lengths
+// adapted from https://stackoverflow.com/a/59905715
+macro_rules! const_array {
+    ($name: ident: $ty: ty = $value: expr) => {
+        const $name: [$ty; $value.len()] = $value;
+    }
+}
+
 // Convenience: use sqrt() as a function to get the square root of
 // anything that can be losslessly converted to f64, since we happen
 // to always want our sqrts to be f64.
@@ -299,9 +307,9 @@ fn load_pointed(assembly: &Assembly) {
 //   A-C   -0.25 * φ^2 = -0.6545084971874737
 fn load_tridiminished_icosahedron(assembly: &Assembly) {
     // create the vertices
-    const COLOR_A: ElementColor = [1.00_f32, 0.25_f32, 0.25_f32];
-    const COLOR_B: ElementColor = [0.75_f32, 0.75_f32, 0.75_f32];
-    const COLOR_C: ElementColor = [0.25_f32, 0.50_f32, 1.00_f32];
+    const COLOR_A: ElementColor = [1.00, 0.25, 0.25];
+    const COLOR_B: ElementColor = [0.75, 0.75, 0.75];
+    const COLOR_C: ElementColor = [0.25, 0.50, 1.00];
     let vertices = [
         Point::new("a1", "A₁", COLOR_A, point( 0.25,  0.75,  0.75)),
         Point::new("a2", "A₂", COLOR_A, point( 0.75,  0.25,  0.75)),
@@ -318,7 +326,7 @@ fn load_tridiminished_icosahedron(assembly: &Assembly) {
     }
     
     // create the faces
-    const COLOR_FACE: ElementColor = [0.75_f32, 0.75_f32, 0.75_f32];
+    const COLOR_FACE: ElementColor = [0.75, 0.75, 0.75];
     const SQRT_1_6: f64 = invsqrt(6.);
     const SQRT_2_3: f64 = 2. * SQRT_1_6;
     let faces = [
@@ -442,8 +450,8 @@ fn load_dodecahedral_packing(assembly: &Assembly) {
     const COLOR_C: ElementColor = [0.25_f32, 0.00_f32, 1.00_f32];
     const PHI_INV: f64 = 1.0 / PHI;
     const COORD_SCALE: f64 = sqrt(PHI + 2.0);
-    const FACE_SCALES: [f64; 2] = [PHI_INV, (13.0 / 12.0) / COORD_SCALE];
-    const FACE_RADII: [f64; 2] = [PHI_INV, 5.0 / 12.0];
+    const_array!(FACE_SCALES: f64 = [PHI_INV, (13.0 / 12.0) / COORD_SCALE]);
+    const_array!(FACE_RADII: f64 = [PHI_INV, 5.0 / 12.0]);
     let mut faces = Vec::<Rc<dyn Element>>::new();
     let subscripts = ["₀", "₁"];
     for j in 0..2 {
@@ -652,7 +660,7 @@ fn load_radius_ratio(assembly: &Assembly) {
     let index_range = 1..=4;
     
     // create the spheres
-    const GRAY: ElementColor = [0.75_f32, 0.75_f32, 0.75_f32];
+    const GRAY: ElementColor = [0.75, 0.75, 0.75];
     let spheres = [
         Sphere::new(
             "sphere_faces".to_string(),
@@ -891,7 +899,7 @@ const F: bool = false; // Free
 // Initial data for the vertices commmon to 554aug2 and 554domed.
 // Used the Vectornaut near_miss branch final positions for 554aug2,
 // to the 3 decimal places currently shown.
-const ACRON554_COMMON: [(&str, (f64, f64, f64), bool, usize, &str); 38] = [
+const_array!(ACRON554_COMMON: (&str, (f64, f64, f64), bool, usize, &str) = [
     // id,       coordinates,  Pin/Free, level, earlier neighbor IDs.
     ("A_NE", ( 0.5,    0.5,   0.),      P, 0, ""),
     ("A_NW", (-0.5,    0.5,   0.),      P, 0, ""),
@@ -931,9 +939,9 @@ const ACRON554_COMMON: [(&str, (f64, f64, f64), bool, usize, &str); 38] = [
     ("G_8",  (-1.19,  -0.517, 3.312),   F, 8, "E_W,F_SW,G_7"),
     ("G_10", (-1.19,   0.483, 3.318),   F, 8, "E_W,F_NW,G_8"),
     ("G_11", (-0.483,  1.19,  3.318),   F, 8, "E_N,F_NW,G_1,G_10"),
-];
+]);
 
-const LEVEL_COLORS: [[f32; 3]; 9] = [
+const_array!(LEVEL_COLORS: ElementColor = [
     [0.75, 0.,   0.75],
     [1.,   0.4,  0.6],
     [1.,   0.,   0.25],
@@ -943,7 +951,7 @@ const LEVEL_COLORS: [[f32; 3]; 9] = [
     [0.25, 0.75, 0.],
     [0.,   0.5,  0.75],
     [0.25, 0.,   1.],
-];
+]);
 
 fn load_554aug2(assembly: &Assembly) {
     for (id, v, _pinned, level, _neighbors) in ACRON554_COMMON {