public void MathExpressionContext_Can_Define_And_Resolve_Expression()
{
MathExpressionContext context = new MathExpressionContext();
context.Define("x", 5);
context.Define("y", MathExpression.Parse("5x"));
Assert.AreEqual(25, context.Resolve("y").Evaluate(context));
}
public void MathExpressionContext_Cannot_Define_Variable_That_Implicitly_Refers_To_Itself()
{
MathExpressionContext context = new MathExpressionContext();
context.Define("x", 5);
context.Define("y", MathExpression.Parse("5x"));
var exception = Assert.Throws<MathExpressionException>(() => context.Define("x", MathExpression.Parse("y")));
Assert.AreEqual("Variable 'x' is refering to itself recursively.", exception.Message);
}
public void MathExpressionContext_Can_Forget_Variable()
{
MathExpressionContext context = new MathExpressionContext();
context.Define("x", 42);
Assert.AreEqual(42, context.Resolve("x").Evaluate(context));
context.Forget("x");
var exception = Assert.Throws<MathExpressionException>(() => context.Resolve("x"));
Assert.AreEqual("The variable 'x' has not been defined.", exception.Message);
}
public void MathExpressionParser_Can_Parse_And_Evaluate_Variable()
{
var input = this.GetPostfixTokenStream("x");
MathExpressionParser parser = new MathExpressionParser();
MathExpression expression = parser.Parse(input);
MathExpressionContext context = new MathExpressionContext();
context.Define("x", 42);
Assert.AreEqual(42D, expression.Evaluate(context));
}
public void MathExpressionContext_Can_Redefine_Variable()
{
MathExpressionContext context = new MathExpressionContext();
context.Define("x", 42);
Assert.AreEqual(42, context.Resolve("x").Evaluate(context));
context.Define("x", 107);
Assert.AreEqual(107, context.Resolve("x").Evaluate(context));
}
public void MathExpressionContext_Variable_Declarations_Can_Occur_In_Any_Order()
{
MathExpression expression = MathExpression.Parse("10+x");
MathExpressionContext context = new MathExpressionContext();
context.Define("x", MathExpression.Parse("5y"));
context.Define("y", 3);
double result = expression.Evaluate(context);
Assert.AreEqual(25, result);
}
public void MathExpression_Can_Evaluate_Variable_Expression()
{
var expression = new VariableExpression("x");
var visitor = new EvaluationVisitor();
var context = new MathExpressionContext();
context.Define("x", 42D);
Assert.AreEqual(42, visitor.Evaluate(expression, context));
}
