public static bool?Evaluate(ExpressionSyntacticElement exp, PredicateList state)
{
if (exp.GetType() == typeof(NotExpression))
{
return(ExpressionExecutive.Evaluate((NotExpression)exp, state));
}
if (exp.GetType() == typeof(AndExpression))
{
return(ExpressionExecutive.Evaluate((AndExpression)exp, state));
}
if (exp.GetType() == typeof(OrExpression))
{
return(ExpressionExecutive.Evaluate((OrExpression)exp, state));
}
if (exp.GetType() == typeof(XorExpression))
{
return(ExpressionExecutive.Evaluate((XorExpression)exp, state));
}
if (exp.GetType() == typeof(PredicateExpression))
{
return(ExpressionExecutive.Evaluate((PredicateExpression)exp, state));
}
if (exp.GetType() == typeof(ImplicationSyntacticExpression))
{
return(ExpressionExecutive.Evaluate((ImplicationSyntacticExpression)exp, state));
}
if (exp.GetType() == typeof(IfAndOnlyIfSyntacticExpression))
{
return(ExpressionExecutive.Evaluate((IfAndOnlyIfSyntacticExpression)exp, state));
}
throw new UnknownExpressionException();
}
/// <summary>
/// Implies when run, evaluates left hand side and right hand side then sets itself
/// this is the a result, True, the argument is valid and false it is not valid.
/// Unknown will have to be taken as invalid. If all steps in the argument are valid
/// then we should have a good argument
/// implies testing
/// p --> q
/// 1 1 1
/// 1 0 0
/// 0 1 1
/// 0 1 0
/// X 1 1
/// X 0 X
/// 1 X X
/// 0 X 1
/// X X X
/// </summary>
/// <param name="element"></param>
/// <param name="predicateState"></param>
/// <returns></returns>
public static PredicateList execute(ImplicationSyntacticExpression element, PredicateList predicateState)
{
bool?lhs = ExpressionExecutive.Evaluate(element.lhs, predicateState);
bool?rhs = ExpressionExecutive.Evaluate(element.rhs, predicateState);
element.Value = ImpliesTruthTable(lhs, rhs);
return(predicateState);
}
public static bool?Evaluate(NotExpression exp, PredicateList state)
{
bool?val = ExpressionExecutive.Evaluate(exp.expression, state);
if (val == true)
{
return(false);
}
if (val == false)
{
return(true);
}
if (val == null)
{
return(null);
}
throw new NotImplementedException();
}
public static bool?Evaluate(IfAndOnlyIfSyntacticExpression exp, PredicateList state)
{
bool?lhs = ExpressionExecutive.Evaluate(exp.lhs, state);
bool?rhs = ExpressionExecutive.Evaluate(exp.rhs, state);
if (lhs == true && rhs == true)
{
return(true);
}
if (lhs == true && rhs == false)
{
return(false);
}
if (lhs == true && rhs == null)
{
return(null);
}
if (lhs == false && rhs == true)
{
return(false);
}
if (lhs == false && rhs == false)
{
return(true);
}
if (lhs == false && rhs == null)
{
return(null);
}
if (lhs == null && rhs == true)
{
return(null);
}
if (lhs == null && rhs == false)
{
return(null);
}
if (lhs == null && rhs == null)
{
return(null);
}
throw new NotImplementedException();
}
/// <summary>
/// each of the following expressions all rely on expressions either unary or binary
/// these are defined in the evaluate function, these can only really be worked out when all predicate suppositions
/// are made. For propositions like p and not p must be run
/// </summary>
/// <param name="element"></param>
/// <param name="predicateState"></param>
/// <returns></returns>
public static PredicateList execute(ThereforeSyntacticElement element, PredicateList predicateState)
{
// for of a therefore are
element.Value = ExpressionExecutive.Evaluate(element.expression, predicateState);
return(predicateState);
}
