Add stubs for MathNumber.

src/renderer/context_element.rs

@@ -5,6 +5,10 @@ use crate::renderer::errors::WalkError;
 use crate::renderer::DustRenderer;
 use std::any::Any;
 use std::ops::Add;
+use std::ops::Div;
+use std::ops::Mul;
+use std::ops::Rem;
+use std::ops::Sub;
 use std::rc::Rc;
 use std::{cmp::Ordering, fmt::Debug};
 
@@ -104,6 +108,38 @@ impl<'a> Add<&'a dyn ContextElement> for &'a dyn ContextElement {
     }
 }
 
+impl<'a> Sub<&'a dyn ContextElement> for &'a dyn ContextElement {
+    type Output = Option<IceResult<'a>>;
+
+    fn sub(self, other: &'a dyn ContextElement) -> Self::Output {
+        self.math_subtract(other)
+    }
+}
+
+impl<'a> Mul<&'a dyn ContextElement> for &'a dyn ContextElement {
+    type Output = Option<IceResult<'a>>;
+
+    fn mul(self, other: &'a dyn ContextElement) -> Self::Output {
+        self.math_multiply(other)
+    }
+}
+
+impl<'a> Div<&'a dyn ContextElement> for &'a dyn ContextElement {
+    type Output = Option<IceResult<'a>>;
+
+    fn div(self, other: &'a dyn ContextElement) -> Self::Output {
+        self.math_divide(other)
+    }
+}
+
+impl<'a> Rem<&'a dyn ContextElement> for &'a dyn ContextElement {
+    type Output = Option<IceResult<'a>>;
+
+    fn rem(self, other: &'a dyn ContextElement) -> Self::Output {
+        self.math_modulus(other)
+    }
+}
+
 pub trait FromContextElement {
     fn from_context_element(&self) -> &dyn IntoContextElement;
 }