private static ICallable BuildFactorialFunction()
{
IExpression condition = new CompareExpression(ComparisonOperator.LessEqual, new VariableExpression("n"), new ConstantExpression(1));
ICommand return1 = new ReturnCommand(new ConstantExpression(1));
ICommand return2 = new ReturnCommand(new ArithmeticBinaryExpression(
ArithmeticOperator.Multiply,
new VariableExpression("n"),
new InvokeExpression("Factorial", new IExpression[] { new ArithmeticBinaryExpression(ArithmeticOperator.Subtract, new VariableExpression("n"), new ConstantExpression(1)) })));
ICommand ifcmd = new IfCommand(condition, return1, return2);
ICallable factorial = new Function(new string[] { "n" }, ifcmd);
return factorial;
}
public void ExecuteIfCommandWhenTrue()
{
IExpression condition = new ConstantExpression(true);
ICommand setCommand = new SetVariableCommand("x", new ConstantExpression(1));
IfCommand command = new IfCommand(condition, setCommand);
BindingEnvironment environment = new BindingEnvironment();
command.Execute(environment);
Assert.AreEqual(1, environment.GetValue("x"));
}
public void ExecuteIfCommandElseWhenFalse()
{
IExpression condition = new ConstantExpression(false);
ICommand setXCommand = new SetVariableCommand("x", new ConstantExpression(1));
ICommand setYCommand = new SetVariableCommand("y", new ConstantExpression(2));
IfCommand command = new IfCommand(condition, setXCommand, setYCommand);
BindingEnvironment environment = new BindingEnvironment();
command.Execute(environment);
Assert.IsNull(environment.GetValue("x"));
Assert.AreEqual(2, environment.GetValue("y"));
}
