wires: half an index impl

hdl/src/wires/index.rs

@@ -0,0 +1,32 @@
+use super::{BitCountType, Wire};
+
+use core::ops::{Index, IndexMut};
+
+// Warning! Indexes by byte (not bit). This isn't very useful.
+impl<const B: BitCountType, const S: usize> Index<usize> for Wire<{B}, {S}> {
+    type Output = u8;
+
+    fn index(&self, idx: usize) -> &u8 {
+        &self.repr[idx]
+    }
+}
+
+impl<const B: BitCountType, const S: usize> IndexMut<usize> for Wire<{B}, {S}> {
+    fn index_mut(&mut self, idx: usize) -> &mut u8 {
+        &mut self.repr[idx]
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::w;
+
+    #[test]
+    fn index_bytes() {
+        assert_eq!(w!(1#0)[0], 0u8);
+        assert_eq!(w!(8*8)[7], 0u8);
+        assert_eq!(w!((8*7)#core::u64::MAX)[7], 255u8);
+    }
+}

hdl/src/wires/mod.rs

@@ -10,6 +10,7 @@
 
 mod conversions;
 mod fmt;
+mod index;
 
 use core::mem::{size_of, MaybeUninit};