static Exp nlLogic_parseExpression(S s) {
  L<S> tok = javaTokPlusBrackets(s);
  
  // a && b
  PairS p = splitAtTokens_once(tok, ll("&", "", "&"));
  if (p != null)
    ret And(nlLogic_parseExpression(first(p)), nlLogic_parseExpression(second(p)));
    
  // function
  if (l(tok) == 5 && isIdentifier(tok.get(1)) && isRoundBracketed(tok.get(3)))
    ret Func(tok.get(1), nlLogic_parseExpression(deRoundBracket(tok.get(3))));
  
  // a = b
  LS l = splitAtTokens(tok, ll("="));
  if (l(l) == 2)
    ret Eq(nlLogic_parseExpression(first(l)), nlLogic_parseExpression(second(l)));
    
  // default
  ret Sentence2(l(tok) == 3 && isQuoted(tok.get(1)) ? unquote(first(tok) : join(tok)));
}