VEC_$REC2                         Domain/OS                          VEC_$REC2


NAME
     vec_$rec2 - calculate second-order linear recurrence of single-precision
     vector

SYNOPSIS (C)
     #include <apollo/base.h>
     #include <apollo/vec.h>

     void vec_$rec2(
          float *start_vec,
          float *vec_2,
          float *vec_3,
          long int &count,
          float *result_vec)

SYNOPSIS (Pascal)
     %include '/sys/ins/base.ins.pas';
     %include '/sys/ins/vec.ins.pas';

     procedure vec_$rec2(
          in start_vec: univ vec_$real_vector;
          in vec_2: univ vec_$real_vector;
          in vec_3: univ vec_$real_vector;
          in count: integer32;
          var result_vec: univ vec_$real_vector);

SYNOPSIS (FORTRAN)
     %include '/sys/ins/base.ins.ftn'
     %include '/sys/ins/vec.ins.ftn'

           parameter (nvec = 10)

           real start_vec(nvec), result_vec(nvec), vec_2(nvec), vec_3(nvec)
           integer*4 count

           call vec_$rec2(start_vec, vec_2, vec_3, count, result_vec)

DESCRIPTION
     Vec_$rec2 calculates a second-order linear recurrence based on start_vec,
     vec_2, and vec_3.

     This routine reads the first and second entries in the array result_vec;
     it then writes count entries into result_vec based on the following for-
     mula:

     For each integer I such that 1 <= I <= count,
     result_vec(I+2) = start_vec(I) + (vec_2(I) x result_vec(I+1))
                        + (vec_3(I) x result_vec(I))

     Notice that result_vec is used both for input and output, and that it
     must be large enough to hold count + 2 entries.

     start_vec
          An input vector.

     vec_2
          An input vector.

     vec_3
          An input vector.

     count
          The number of elements to be operated on.

     result_vec
          The vector containing two input variables and the output from the
          recurrence calculations.

NOTES
     When vec_$rec2 is used to operate on matrixes in C and Pascal, start_vec,
     vec_2, vec_3, and result_vec are row vectors; in FORTRAN, they are column
     vectors.

     As in all the vec_$ calls,  the result array must not overlap any of the
     input arrays; the result array may be identical to an input, but must not
     contain any smaller subset of an input.   Because of pipelining, using
     overlapping input and output arrays may cause incorrect results.


SEE ALSO
     vec_$rec2c, vec_$rec2_i, vec_$drec2, vec_$drec2_i, vec_$irec2,
     vec_$irec2_i, vec_$irec216, vec_$irec216_i.