bool ProcessForNextState(Interpreter interpreter, ForNextLoopState forNextState, VariableNameToken variableNameToken = null)
{
// For NEXT with a variable name, check the variable name matches the one stored in the stack
// if (variableNameToken != null && (forNextState.VariableNameToken.Name != variableNameToken.Name))
// throw new Exceptions.NextWithoutForException();
if (variableNameToken != null && (forNextState.VariableNameToken.Name != variableNameToken.Name))
{
/* Get Calendar from David Ahl's BASIC Computer Games to work without producing
* a NEXT WITHOUT FOR error. If the variable in NEXT [x] is not on top of the stack
* like it should be, then pop variables off the stack until a name match is found.
* If still no match, only then produce a NEXT WITHOUT FOR error. This supports the case
* where the program GOTOs out of an inner loop to an outer loop.
*/
interpreter.ForNextLoops.Pop();
while (interpreter.ForNextLoops.Count > 0)
{
forNextState = interpreter.ForNextLoops.Peek();
if (forNextState.VariableNameToken.Name == variableNameToken.Name)
{
break;
}
// Discard this loop and try matching the next one
interpreter.ForNextLoops.Pop();
}
if (interpreter.ForNextLoops.Count == 0)
{
throw new Exceptions.NextWithoutForException();
}
}
var newValue = forNextState.CurrentValue.RealValue + forNextState.StepValue.RealValue;
bool forNextLoopIsDone = false;
if (forNextState.StepValue.RealValue >= 0)
{
forNextLoopIsDone = (newValue > forNextState.EndValue.RealValue);
}
else
{
forNextLoopIsDone = (newValue < forNextState.EndValue.RealValue);
}
if (forNextLoopIsDone)
{
interpreter.ForNextLoops.Pop();
return(true);
}
#if false
// If done, pop the stack and return true
if (forNextState.StartValue.RealValue <= forNextState.EndValue.RealValue)
{
if (newValue > forNextState.EndValue.RealValue)
{
interpreter.ForNextLoops.Pop();
return(true);
}
}
else
{
var endValue = forNextState.EndValue.RealValue;
bool isLessThan = (newValue < endValue);
if (newValue > forNextState.EndValue.RealValue)
{
interpreter.ForNextLoops.Pop();
return(true);
}
}
#endif
// Keep going, set the NEXT variable and goto the first statement after the FOR
forNextState.CurrentValue = interpreter.TokensProvider.CreateRealValueToken(newValue);
interpreter.VariablesEnvironment.SetVariableValue(forNextState.VariableNameToken, forNextState.CurrentValue);
if (forNextState.LoopMarker != null)
{
// If in immediate mode, there may be no valid statement to loop to.
if (forNextState.LoopMarker.Valid)
{
var forNextStatement = new StatementMarker(forNextState.LoopMarker);
interpreter.NextStatementMarker = forNextStatement;
}
}
else
{
var index = forNextState.ImmediateModeStatementIndex;
interpreter.CurrentImmediateModeStatementMarker.MoveTo(index);
}
// Not done
return(false);
}
public override void Execute(Interpreter interpreter, TokenMarker tokenMarker)
{
if (!(tokenMarker.Token is VariableNameToken variableNameToken))
{
throw new Exceptions.SyntaxErrorException();
}
if (variableNameToken.VariableType != VariableValueType.RealNumber)
{
throw new Exceptions.SyntaxErrorException();
}
if (!(tokenMarker.GetNextToken() is EqualToken))
{
throw new Exceptions.SyntaxErrorException();
}
tokenMarker.MoveNext();
NumericValueToken startValue;
try
{
startValue = (NumericValueToken)interpreter.ExpressionEvaluator.Evaluate(tokenMarker);
}
catch (InvalidCastException)
{
throw new Exceptions.TypeMismatchException();
}
if (!(tokenMarker.Token is ToToken))
{
throw new Exceptions.SyntaxErrorException();
}
tokenMarker.MoveNext();
NumericValueToken endValue;
try
{
endValue = (NumericValueToken)interpreter.ExpressionEvaluator.Evaluate(tokenMarker);
}
catch (InvalidCastException)
{
throw new Exceptions.TypeMismatchException();
}
NumericValueToken stepValueToken = null;
if (tokenMarker.Token != null)
{
if (!(tokenMarker.Token is StepToken))
{
throw new Exceptions.SyntaxErrorException();
}
tokenMarker.MoveNext();
var result = interpreter.ExpressionEvaluator.Evaluate(tokenMarker);
if (!(result is NumericValueToken))
{
throw new Exceptions.TypeMismatchException();
}
stepValueToken = (NumericValueToken)result;
}
else
{
// Default step is 1 or -1
// if (startValue.RealValue <= endValue.RealValue)
stepValueToken = interpreter.TokensProvider.CreateRealValueToken(1);
// else
// stepValueToken = interpreter.TokensProvider.CreateRealValueToken(-1);
}
ForNextLoopState forNextLoopState;
if (interpreter.InterpreterMode == InterpreterMode.Running)
{
var forNextMarker = interpreter.CopyCurrentStatementMarker();
// In immediate mode, FOR may not neccessarily be followed by a statement.
if (forNextMarker.Valid)
{
forNextMarker.MoveToNextStatement();
}
forNextLoopState = new ForNextLoopState(forNextMarker, variableNameToken, startValue, endValue, stepValueToken);
}
else
{
var index = interpreter.CurrentImmediateModeStatementMarker.StatementIndex;
forNextLoopState = new ForNextLoopState(index, variableNameToken, startValue, endValue, stepValueToken);
}
interpreter.ForNextLoops.Push(forNextLoopState);
interpreter.VariablesEnvironment.SetVariableValue(variableNameToken, startValue);
}
