public function next()
{
$buffer = '';
for ($this->position = 0; $this->position < count($this->input); $this->position++) {
$char = $this->input[$this->position];
$code = ord($char);
if ($code <= 0x20) {
// whitespace & control characters
continue;
} elseif ($code >= 0x30 && $code <= 0x39) {
// digits
$buffer .= $char;
$next = $this->peek(function ($ord) {
return $ord >= 0x30 && $ord <= 0x39;
});
if ($next) {
// digit continued
continue;
} else {
(yield ['symbol' => Symbol::INTEGER(), 'value' => (int) $buffer]);
$buffer = '';
}
} elseif ($code === 0x2a || $code === 0x2b || $code === 0x2d || $code === 0x2f) {
// operators + - * /
(yield ['symbol' => Symbol::OPERATOR(), 'value' => $char]);
} elseif ($code === 0x28) {
(yield ['symbol' => Symbol::LPAREN(), 'value' => $char]);
} elseif ($code === 0x29) {
(yield ['symbol' => Symbol::RPAREN(), 'value' => $char]);
} else {
throw new SyntaxException("Syntax error on position {$this->position}: unexpected token '{$char}'!");
}
}
}