implement integer division to an extent

src/value/ops.rs

@@ -233,10 +233,22 @@ impl Div for Value {
             Self::Null => todo!(),
             Self::Dimension(num, unit) => match other {
                 Self::Dimension(num2, unit2) => {
+                    if !unit.comparable(&unit2) {
+                        return Err(format!("Incompatible units {} and {}.", unit2, unit).into());
+                    }
                     if unit == unit2 {
                         Value::Dimension(num / num2, Unit::None)
+                    } else if unit == Unit::None {
+                        todo!("inverse units")
+                    } else if unit2 == Unit::None {
+                        Value::Dimension(num / num2, unit)
                     } else {
-                        todo!("unit conversions")
+                        Value::Dimension(
+                            num / (num2
+                                * UNIT_CONVERSION_TABLE[&unit.to_string()][&unit2.to_string()]
+                                    .clone()),
+                            Unit::None,
+                        )
                     }
                 }
                 Self::Ident(s, q) => Value::Ident(

tests/division.rs

@@ -0,0 +1,30 @@
+#![cfg(test)]
+
+#[macro_use]
+mod macros;
+
+test!(
+    none_div_none,
+    "a {\n  color: (35 / 7);\n}\n",
+    "a {\n  color: 5;\n}\n"
+);
+test!(
+    unit_div_none,
+    "a {\n  color: (35% / 7);\n}\n",
+    "a {\n  color: 5%;\n}\n"
+);
+test!(
+    unit_div_unit,
+    "a {\n  color: (35% / 7%);\n}\n",
+    "a {\n  color: 5;\n}\n"
+);
+test!(
+    unit_conversion,
+    "a {\n  color: (35px / 7in);\n}\n",
+    "a {\n  color: 0.0520833333;\n}\n"
+);
+// error!(
+//     none_div_unit,
+//     "a {\n  color: (35 / 7%);\n}\n",
+//     "Error: 5%^-1 isn't a valid CSS value."
+// );