class LexError(Exception):
    pass


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

    def __repr__(self):
        return f"{self.kind}({self.value!r})"

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


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


def tokenize(src: str) -> list:
    tokens = []
    i = 0
    while i < len(src):
        ch = src[i]

        if ch in ' \t':
            i += 1
            continue

        if ch.isdigit() or ch == '.':
            j = i
            has_dot = False
            while j < len(src) and (src[j].isdigit() or (src[j] == '.' and not has_dot)):
                if src[j] == '.':
                    has_dot = True
                j += 1
            num_str = src[i:j]
            if num_str == '.':
                raise LexError(f"Invalid character '.' at position {i}")
            value = float(num_str) if has_dot else int(num_str)
            tokens.append(Token('NUMBER', value))
            i = j
            continue

        if ch in _SINGLE:
            tokens.append(Token(_SINGLE[ch], ch))
            i += 1
            continue

        raise LexError(f"Invalid character {ch!r} at position {i}")

    tokens.append(Token('EOF', None))
    return tokens