private ITripleExpression Atomic()
{
GetNext();
ITripleExpression ret;
switch (current)
{
case State.number:
ret = new Const(constant);
GetNext();
break;
case State.variable:
ret = new Variable(Char.ToString(variable));
GetNext();
break;
case State.minus:
ret = new CheckedSubtract(new Const(0), Atomic());
break;
case State.abs:
ret = new CheckedAbs(Atomic());
break;
case State.sqrt:
ret = new Square(Atomic());
break;
case State.lparen:
ret = AddSubt();
if (current != State.rparen)
{
Console.WriteLine(") missing");
throw new InvalidOperationException(") missing");
}
GetNext();
break;
default:
ret = null;
Console.WriteLine("Unrecognizable format");
throw new InvalidOperationException("Unrecognizable format");
break;
}
return(ret);
}
private ITripleExpression AddSubt()
{
ITripleExpression left = MulDiv();
while (true)
{
switch (current)
{
case State.minus:
left = new CheckedSubtract(left, MulDiv());
break;
case State.plus:
left = new CheckedAdd(left, MulDiv());
break;
default:
return(left);
}
}
}