a # 1 60 R ' cmatrix                                                    '
a # a,[1]  ' C''a#matrix a''if 0^=RRa                                     '
a # a,[1]  ' C''b#matrix b''if 0^=RRb                                     '
a # a,[1]  ' $0                                                         '
a # a,[1]  '"cmatrix is used by e.g. ccat.                              '
a # a,[1]  '"from ''the apl handbook of techniques'' copyright 1978, ibm. '
a # a,[1]  '"assumes localized a and b.                                 '
Lfx a