a # 1 60 R ' l#firstm m                                                 '
a # a,[1]  ' l#V`/<\m&.=Tm                                              '
a # a,[1]  ' $0                                                         '
a # a,[1]  '"firstm - select first or only appearance in matrix         '
a # a,[1]  '"from ''the apl handbook of techniques'' copyright 1978, ibm. '
a # a,[1]  '" returns logic vector that can select:                     '
a # a,[1]  '"-rows of a matrix, ignoring duplicates                     '
a # a,[1]  '"-their indices                                             '
a # a,[1]  '"-corresponding rows of inverted files                      '
a # a,[1]  '" see Griota                                                '
Lfx a