public override object Evaluate(IEvaluationContext context = null)
{
if (context == null)
{
context = Expression.DefaultContext;
}
if (_Operator == "=") //Assignment
{
if (!(_OperandA is ReferenceExpression))
{
throw new ExpressionException("The left-hand side of an assignment must be a variable.");
}
if (_OperandB.ContainsReference(_OperandA.Description))
{
throw new ExpressionException("Cannot assign an expression to a variable that contains a reference to that same variable. Use := operator to assign current value.");
}
context.SetVariable(_OperandA.Description, _OperandB);
return(_OperandB.Evaluate(context));
}
else if (_Operator == ":=") // Assign current value
{
if (!(_OperandA is ReferenceExpression))
{
throw new ExpressionException("The left-hand side of an assignment must be a variable.");
}
object result = _OperandB.Evaluate(context);
context.SetVariable(_OperandA.Description, new ValueExpression(result?.ToString(), result));
return(result);
}
else
{
dynamic valueA = _OperandA.Evaluate(context);
dynamic valueB = _OperandB.Evaluate(context);
//TODO: Check units
switch (_Operator)
{
case "+":
return(valueA + valueB);
case "-":
return(valueA - valueB);
case "*":
case ".":
return(valueA * valueB); //TODO: Set units
case "/":
case "÷":
return(valueA / valueB);
case "==":
case "↔":
case "≡":
return(valueA == valueB);
case "!=":
case "≠":
return(valueA != valueB);
case ">":
return(valueA > valueB);
case ">=":
case "≥":
return(valueA >= valueB);
case "<":
return(valueA < valueB);
case "<=":
case "≤":
return(valueA <= valueB);
case "AND":
case "^":
case "&":
return(valueA & valueB);
case "OR":
case "˅":
return(valueA || valueB);
case "NAND":
case "↑":
return(!(valueA & valueB));
case "NOR":
case "↓":
return(!(valueA | valueB));
case "XOR":
case "⊕":
return(valueA ^ valueB);
case "²":
return(valueA * valueA * valueB);
case "³":
return(valueA * valueA * valueA * valueB);
}
}
throw new ExpressionException("Invalid syntax. Expression could not be evaluated.");
}
public void SetValue(object newValue)
{
_evaluationContext.SetVariable(_name, newValue);
}
public void SetVariable(string name, object value)
{
_relatedContext.SetVariable(name, value);
}