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 VariableFinderVisitor_Can_Find_Variable_That_Is_Negated()
{
// Verifies fix for bug that caused negated expression
// to be skipped in expression visitor.
var expression = MathExpression.Parse("10+(-x)");
var context = new MathExpressionContext();
var visitor = new VariableFinderVisitor();
Assert.IsTrue(visitor.HasVariableDefined(expression, context, "x"));
}
public void VisitMathExpression(MathExpressionContext context)
{
VisitExpression(context.left);
builder.OutputOperation(Operation.OpPush, 0);
VisitExpression(context.right);
builder.OutputOperation(Operation.OpPop, 1);
var symbol = "";
if (context.type != null)
{
symbol = context.type.Text;
}
if (context.comparison_operator() != null)
{
symbol = context.comparison_operator().GetText();
}
switch (symbol)
{
case "+":
builder.OutputOperation(Operation.OpAdd);
break;
case "-":
builder.OutputOperation(Operation.OpSub);
break;
case "*":
builder.OutputOperation(Operation.OpMul);
break;
case "/":
builder.OutputOperation(Operation.OpDiv);
break;
case "&&":
builder.OutputOperation(Operation.OpAnd);
break;
case "||":
builder.OutputOperation(Operation.OpOr);
break;
case "==":
builder.OutputOperation(Operation.OpEquals);
break;
case "<":
builder.OutputOperation(Operation.OpLessThan);
break;
case ">":
builder.OutputOperation(Operation.OpGreaterThan);
break;
case "<=":
builder.OutputOperation(Operation.OpLessThanOrEquals);
break;
case ">=":
builder.OutputOperation(Operation.OpGreaterOrEquals);
break;
default:
throw new Exception($"Unhandled math operation {symbol}");
}
}
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 VariableFinderContext(MathExpressionContext expressionContext, string variable)
{
_expressionContext = expressionContext;
_variable = variable;
_found = false;
}
public void MathExpressionContext_Undefined_Variable_Throws()
{
MathExpressionContext context = new MathExpressionContext();
var exception = Assert.Throws<MathExpressionException>(() => context.Resolve("x"));
Assert.AreEqual("The variable 'x' has not been defined.", exception.Message);
}
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));
}
public EvaluationContext(MathExpressionContext context)
{
_expressionContext = context;
_result = 0;
}
