VEC_$DREC1R                       Domain/OS                        VEC_$DREC1R


NAME
     vec_$drec1r - function returning first-order linear recurrence of
     double-precision vector

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

     double vec_$drec1r(
          double *start_vec,
          double *vec_2,
          long int &count,
          double &init_value)

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

     function vec_$drec1r(
          in start_vec: univ vec_$double_vector;
          in vec_2: univ vec_$double_vector;
          in count: integer32;
          in init_value: double):double;

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

           parameter (nvec = 10)

           real*8 start_vec(nvec), vec_2(nvec), init_value, return_value
           integer*4 count

           return_value = vec_$drec1r(start_vec, vec_2, count, init_value)

DESCRIPTION
     Vec_$drec1r calculates a first-order linear recurrence based on
     start_vec, with coefficients taken from vec_2.  Unlike vec_$rec1, it does
     not produce an output vector.  Instead, it calculates the value of each
     entry in a temporary output vector, then returns the value of the last
     entry.  It differs from vec_$rec1r in that the vectors being handled are
     double-precision floating point.

     This routine sets its return value to init_value; it then performs a
     recurrence calculation as follows:

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

     start_vec
          An input vector.

     vec_2
          An input vector.

     count
          The number of elements to be operated on.

     init_value
          The initial value on which the recurrence calculation is based.

NOTES
     When vec_$drec1r is used to operate on matrixes in C and Pascal,
     start_vec and vec_2  are row vectors; in FORTRAN, they are column vec-
     tors.


SEE ALSO
     vec_$rec1, vec_$rec1c, vec_$rec1n, vec_$rec1r, vec_$rec1cr, vec_$rec1r_i,
     vec_$drec1r_i, vec_$irec1r, vec_$irec1r_i, vec_$irec1r16,
     vec_$irec1r16_i.