a # 1 60 R ' r#x riota y                                                '
a # a,[1]  ' y#matrix y H x#matrix x                                    '
a # a,[1]  ' r#Lio++/~V\(((0 1XRx)SRy)Yy)&.=T((0 1XRy)SRx)Yx            '
a # a,[1]  ' $0                                                         '
a # a,[1]  '"                                                           '
a # a,[1]  '"from ''the apl handbook of techniques'' copyright 1978, ibm. '
a # a,[1]  '"-riota extends to matrix arguments the function of dyadic  '
a # a,[1]  '" I (aIb...the least index in vector a of the element(s) in '
a # a,[1]  '" scalar or vector b).                                      '
a # a,[1]  '"-the result r is a vector of the respective row indices of '
a # a,[1]  '" the first occurrence of the rows of y in x, ignoring      '
a # a,[1]  '" trailing blanks.  if a row of y does not occur in x, the  '
a # a,[1]  '" corresponding element of r is set to 1+1YRx.  non-matrix  '
a # a,[1]  '" arguments are reshaped, scalar and vector arguments are   '
a # a,[1]  '" treated as 1-row matrices.                                '
a # a,[1]  '"-uses: Gmatrix Gh                                          '
Lfx a