Operator Sub implemented

src/number.rs

@@ -113,3 +113,31 @@ pub fn add<'x>(a: Number, b: Number) -> VarRef<'x> {
         }
     }
 }
+
+pub fn sub<'x>(a: Number, b: Number) -> VarRef<'x> {
+    use self::NumberInner::*;
+    match (norm(a.0), norm(b.0)) {
+        (I64(a), I64(b)) => {
+            a.checked_sub(b).map(val)
+            .unwrap_or_else(|| val((a as f64) - (b as f64)))
+        }
+        (U64(a), U64(b)) => {
+            a.checked_sub(b).map(val)
+            .unwrap_or_else(|| val((a as f64) - (b as f64)))
+        }
+        (F64(a), F64(b)) => val(a - b),
+        (I64(a), F64(b)) => val(a as f64 - b),
+        (F64(a), I64(b)) => val(a - b as f64),
+        (U64(a), F64(b)) => val(a as f64 - b),
+        (F64(a), U64(b)) => val(a - b as f64),
+        (U64(a), I64(b)) => {
+            a.checked_add((-b as u64)).map(val)
+            .unwrap_or_else(|| val((a as f64) - (b as f64)))
+        }
+        (I64(a), U64(b)) if b < i64::MAX as u64 => {
+            a.checked_sub(b as i64).map(val)
+            .unwrap_or_else(|| val((a as f64) - (b as f64)))
+        }
+        (I64(a), U64(b)) => val((a as f64) - (b as f64)),
+    }
+}

src/render.rs

@@ -134,6 +134,9 @@ fn eval_expr<'x, 'render: 'x>(r: &mut Renderer, root: &SubContext<'x, 'render>,
         ExprCode::Add(ref a, ref b) => {
             operator(number::add, a, b, r, root)
         }
+        ExprCode::Sub(ref a, ref b) => {
+            operator(number::sub, a, b, r, root)
+        }
         ExprCode::And(ref a, ref b) => {
             let left = eval_expr(r, root, a);
             match left.as_bool() {

src/tests/math.rs

@@ -27,3 +27,11 @@ fn render_plus_different_types() {
     assert_eq!(render_x_y("{{ x + y }}", 10u64, -100i64), "-90");
     assert_eq!(render_x_y("{{ x + y }}", -100i64, 10i64), "-90");
 }
+
+#[test]
+fn render_minus() {
+    assert_eq!(render_x_y("{{ x - y }}", 1u32, 1u32), "0");
+    assert_eq!(render_x_y("{{ x - y }}", 10u64, 7u64), "3");
+    assert_eq!(render_x_y("{{ x - y }}", 10i64, -1i64), "11");
+    assert_eq!(render_x_y("{{ x - y }}", 1.5f64, -1f64), "2.5");
+}