Four to finish - 12a Nocturnal arboreal primate native to Indonesia and the Philippines (7 letters) -AR___R, 5d Natives or inhabitants of US state of Indiana (8 letters) H_O___R_, 16d Selection of Chinese foods eaten as an appetiser (3.3) -I_S_M, 18d Rules governing use of statements in a programming language (6 letters) S_N_A_ - thanks in advance!