Document reusable operations

README.md

@@ -18,20 +18,34 @@ decimal result = myCalculator.Evaluate("2 * 3 max 4"); // 8
 
 ### Creating and using variables
 ```csharp
+// Creating a variables collection
 Replacements variables = new Replacements
 {
 	["a"] = 5,
 	["PI"] = 3.1415926535897931
 };
 
-Calculator myCalculator = new Calculator(variables);
+Calculator myCalculator = new Calculator(variables); // default variables collection is optional (can still add variables without a collection)
 
-// Replacing existing variables
+// Replacing or creating variables
 myCalculator.Replace("a", 2);
-myCalculator.Replace("b", 1);
+myCalculator.Replace("b", 1); // new syntax: myCalculator["b"] = 1;
 decimal result = calculator.Evaluate("{a} + 2 * {b} + {PI}"); // 7.1415926535897931
 ```
 
+### Creating and reusing operations
+```csharp
+myCalculator["a"] = 5;
+
+// Creating operations
+OperationInfo op = myCalculator.CreateOperation("2 * {a}");
+decimal result1 = myCalculator.Evaluate(op); // 10
+
+// Reusing the operation (improves performance)
+myCalculator["a"] = 3;
+decimal result2 = myCalculator.Evaluate(op); // 6
+```
+
 ### Using the static api: SMath
 ```csharp
 // Same API as a calculator instance except the Evaluate method