Split out some modules

src/expr.rs

@@ -0,0 +1,16 @@
+
+
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub enum Operator {
+    Plus, Minus, FloatDivision, IntDivision,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum Expr {
+    HexOctalBinary(i64),    // : Int
+    FractionalNumber(f64),  // : Float
+    WholeNumber(i64),       // : Int | Float
+
+    // Functions
+    CallOperator(Operator, Box<Expr>, Box<Expr>),
+}