private string ReadOperator(SymbolSequence op)
{
var x = _chars.GetNext();
if (!char.IsPunctuation(x) && !char.IsSymbol(x))
{
_chars.PutBack(x);
return(op.Operator);
}
var nextOp = op.Get(x);
if (nextOp == null)
{
_chars.PutBack(x);
return(op.Operator);
}
var recurse = ReadOperator(nextOp);
if (recurse != null)
{
return(recurse);
}
_chars.PutBack(x);
if (!string.IsNullOrEmpty(op.Operator))
{
return(op.Operator);
}
return(null);
}
public TokenScanner(ICharacterSequence chars)
{
_chars = chars ?? throw new ArgumentNullException(nameof(chars));
_operators = new SymbolSequence();
// punctuation
_operators.Add(".", ",", ";");
// Parens
_operators.Add("(", ")");
// Arithmetic operators
_operators.Add("+", "-", "/", "*", "&", "|", "^");
// Unary ~. Unary - and + are covered above
_operators.Add("~");
// "=" is both for comparison and assignment
_operators.Add("=");
// Comparison operators
_operators.Add("!=", "<>", ">", "<", ">=", "<=");
// Assignment operators
_operators.Add("+=", "-=", "*=", "/=", "%=", "&=", "^=", "|=");
}
