System.IO.StringReader.Peek C# (CSharp) Méthode

        public override int Peek()
        {
            if (_s == null)
            {
                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
            }
            if (_pos == _length)
            {
                return -1;
            }

            return _s[_pos];
        }

        public IEnumerable<Token> Scan(string expression)
        {
            _reader = new StringReader(expression);

            var tokens = new List<Token>();
            while (_reader.Peek() != -1)
            {
                var c = (char)_reader.Peek();
                if (Char.IsWhiteSpace(c))
                {
                    _reader.Read();
                    continue;
                }

                if (Char.IsDigit(c))
                {
                    var nr = ParseNumber();
                    tokens.Add(new NumberConstantToken(nr));
                }
                else if (c == '-')
                {
                    tokens.Add(new MinusToken());
                    _reader.Read();
                }
                else if (c == '+')
                {
                    tokens.Add(new PlusToken());
                    _reader.Read();
                }
                else
                    throw new Exception("Unknown character in expression: " + c);
            }

            return tokens;
        }