class LexError(Exception):
    pass


class Token:
    __slots__ = ('kind', 'value')

    def __init__(self, kind: str, value):
        self.kind = kind
        self.value = value

    def __repr__(self):
        return f'Token({self.kind!r}, {self.value!r})'

    def __eq__(self, other):
        if isinstance(other, Token):
            return self.kind == other.kind and self.value == other.value
        return NotImplemented


_SINGLE_CHAR = {
    '+': 'PLUS',
    '-': 'MINUS',
    '*': 'STAR',
    '/': 'SLASH',
    '(': 'LPAREN',
    ')': 'RPAREN',
}


def tokenize(src: str) -> list:
    tokens = []
    i = 0
    n = len(src)
    while i < n:
        c = src[i]
        if c in ' \t':
            i += 1
        elif c in _SINGLE_CHAR:
            tokens.append(Token(_SINGLE_CHAR[c], c))
            i += 1
        elif c.isdigit() or c == '.':
            start = i
            has_dot = False
            while i < n and (src[i].isdigit() or (src[i] == '.' and not has_dot)):
                if src[i] == '.':
                    has_dot = True
                i += 1
            num_str = src[start:i]
            try:
                value = float(num_str) if has_dot else int(num_str)
            except ValueError:
                raise LexError(f"Invalid number {num_str!r} at position {start}")
            tokens.append(Token('NUMBER', value))
        else:
            raise LexError(f"Unexpected character {c!r} at position {i}")
    tokens.append(Token('EOF', None))
    return tokens