document type properties

README.md

@@ -0,0 +1,9 @@
+# F8: 8-bit floats
+
+> ⚠️ Not for production use!
+
+F8 is a toy software floating-point math library.
+It provides an 8-bit floating point type `F8`, with 5 mantissa bits, 3 exponent bits, and no sign bit.
+The format used resembles [IEEE 754] binary formats but stripped down to the bare necessities: the only special value supported is zero.
+
+[IEEE 754]: https://en.wikipedia.org/wiki/IEEE_754

src/lib.rs

@@ -31,7 +31,22 @@ const E_BIAS: u8 = E_STORAGE_MAX - E_MAX;
 const M_MASK: u8 = M_STORAGE_MAX;
 const E_MASK: u8 = E_STORAGE_MAX << M_BITS;
 
-/// 8-bit unsigned binary floating-point type, with [`M_BITS`] mantissa bits and [`E_BITS`] exponent bits.
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+/// 8-bit unsigned binary floating-point type.
+///
+/// # Properties
+///
+/// * Mantissa width: 5 bits ([`M_BITS`])
+/// * Exponent width: 3 bits ([`E_BITS`])
+/// * Negative values: not supported
+/// * Zero: special-cased
+/// * Subnormals: not supported
+/// * Infinity: not supported
+/// * NaN: not supported
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Default)]
 #[repr(transparent)]
 pub struct F8(u8);
+
+impl F8 {
+	pub const ZERO: Self = Self(0);
+	pub const ONE: Self = Self::merge(0, E_BIAS);
+}