Expression Evaluator Simple Expressions

The simple expressions are literals such as integer and real numbers and names of variables.

• You can also combine them into complex expressions by using operators.
• Operator precedence and associativity determine the order in which the operations in an expression are performed.
• You can use parentheses to change the order of evaluation imposed by operator precedence and associativity.

The following example evaluates a simple mathematical expression.

public static void Example1()
{
    string expression = "2 + 13";
    ExpressionEvaluator evaluator = new ExpressionEvaluator();
    Console.WriteLine(evaluator.Evaluate(expression));
}

In an expression with multiple operators, the operators with higher precedence are evaluated before the operators with lower precedence.

In the following example, the multiplication is performed first because it has higher precedence than addition.

public static void Example2()
{
    string expression = "2 + 2 * 2";
    CompiledExpression compiledExpression = new CompiledExpression(expression);
    Console.WriteLine(compiledExpression.Eval());
}

You can use the parentheses to change the order of evaluation imposed by operator precedence:

public static void Example3()
{
    string expression = "(2 + 2) * 2";
    CompiledExpression compiledExpression = new CompiledExpression(expression);
    Console.WriteLine(compiledExpression.Eval());
}

You can use the generic and non-generic versions of the CompiledExpression class. In the above examples, we have used the non-genric class, which gives you results of the evaluated expression cast to the type object.

The following example shows the usage of a generic class.

public static void Example4()
{
    string expression = "(2.00 + 2.00) * 2.00";
    CompiledExpression<float> compiledExpression = new CompiledExpression<float>(expression);
    var result = compiledExpression.Eval();
    Console.WriteLine("{0} ({1})", result, result.GetType());
}