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);
}
private static PropositionExpression RunProposition(PropositionExpression pse, LogicArgument program)
{
if (pse is ImplicationSyntacticExpression)
{
ExpressionExecutive.execute((ImplicationSyntacticExpression)pse, program.predicateList);
}
else if (pse is IfAndOnlyIfSyntacticExpression)
{
ExpressionExecutive.execute((IfAndOnlyIfSyntacticExpression)pse, program.predicateList);
}
else
{
throw new NotImplementedException("this bit cannot be reached and records a design error");
}
return(pse);
}
private static PredicateSetterSyntacticElement RunPredicateSetter(PredicateSetterSyntacticElement pse, LogicArgument program)
{
if (pse is PropositionSyntacticElement)
{
program.predicateList = ExpressionExecutive.execute((PropositionSyntacticElement)pse, program.predicateList);
}
else if (pse is PropositionNegationSyntacticElement)
{
program.predicateList = ExpressionExecutive.execute((PropositionNegationSyntacticElement)pse, program.predicateList);
}
else
{ // case cannot currently exist
throw new NotImplementedException();
}
return(pse);
}
//what does this do?
// if the conclusion is known, it works out what the conclusion should be and
// returns the actual conclusion and the given one.
// p->q conclusion is q predicate is p after execution p is known or not depending on value of p
// if both are set then? is the truth table checked? do interested in state before and after
// so how does an implies statement work?
// p --> q ==== !p or q
// 0 1 0
// 0 1 1
// 1 0 0
// 1 1 1
/// <summary>
/// Execute with a full trace of what happened
/// </summary>
/// <param name="program"></param>
public static List <string> Execute(LogicArgument program, out ProgramReturnCode errorCode)
{
// we want a value for the whole program and
// we want a value for each line in the program
// from the start to the end
// executing must suggest a value for a predicate,
// if this value cannot be set
// 1 can be set to 1
// 0 can be set to 0
// ? can be set to anything 1, 0 or ?
// The execution must be such that it runs through setting predicates
// run predicates -- if fails produce result
// run not expressions -- if fails produce result
// run propositions in order
// produce result
List <string> programOutput = new List <string>();
// if no errors
errorCode = Validate(program, ref programOutput);
if (errorCode == ProgramReturnCode.No_errors)
{
errorCode = RunPredicateSetters(program, ref programOutput);
if (errorCode == ProgramReturnCode.No_errors)
{
// run propositions
errorCode = RunPropositions(program, ref programOutput);
if (errorCode == ProgramReturnCode.No_errors)
{
// run therefore statement
ExpressionExecutive.execute(program.thereforeSyntacticElement, program.predicateList);
program.Conclusion = program.thereforeSyntacticElement.Value;
if (program.Conclusion == true)
{
programOutput.Add("Your arguments conclusion was true.");
}
else
{
programOutput.Add("Your arguments conclusion was false.");
}
}
}
}
return(programOutput);
}
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);
}
