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VEC_$SUB_I                        Domain/OS                         VEC_$SUB_I


NAME
     vec_$sub_i - subtract single-precision vectors in matrixes

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

     void vec_$sub_i(
          float *start_vec,
          long int &inc1,
          float *sub_vec,
          long int &inc2,
          long int &length,
          float *result_vec,
          long int &inc3)

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

     procedure vec_$sub_i(
          in start_vec: univ vec_$real_vector;
          in inc1: integer32;
          in sub_vec: univ vec_$real_vector;
          in inc2: integer32;
          in length: integer32;
          out result_vec: univ vec_$real_vector;
          in inc3: integer32);

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

           parameter (nvec = 10)

           real start_vec(nvec), sub_vec(nvec), result_vec(nvec)
           integer*4 length, inc1, inc2, inc3

           call vec_$sub_i(start_vec, inc1, sub_vec, inc2,
          &                length, result_vec, inc3)

DESCRIPTION
     Vec_$sub_i subtracts length elements of sub_vec selected by inc2 from
     length elements of start_vec selected by inc1, and supplies the result in
     the elements of result_vec selected by inc3.

     Through appropriate choice of inc1, inc2, and inc3, a program can use
     vec_$sub_i to subtract individual vectors in two matrixes and place the
     difference in a vector of another matrix.  To subtract the Nth vector in
     matrix Y from the Mth vector in matrix X, choose inc2 equal to the number
     of vectors in matrix Y and inc1 equal to the number of vectors in matrix
     X.  Then place the Mth element of matrix X at the beginning of start_vec,
     and place the Nth element of matrix Y at the beginning of sub_vec.  To
     place the result of the operation in the Pth vector of a resultant
     matrix, choose inc3 equal to the number of vectors in the resultant
     matrix, and place the Pth element of the matrix array at the beginning of
     result_vec.

     In C, the resulting operation is

          j = 0;
          k = 0;
          l = 0;
          for (i = 0; i < length, ++i) {
               result_vec[j] = start_vec[k] - sub_vec[l];
               j += inc3;
               k += inc1;
               l += inc2;
          }

     In Pascal, the resulting operation is

          j := 1;
          k := 1;
          l := 1;
          for i := 1 to length do
               begin
               result_vec[j] := start_vec[k] - sub_vec[l];
               j := j + inc3;
               k := k + inc1;
               l := l + inc2;
               end

     In FORTRAN, the resulting operation is

           j = 1
           k = 1
           l = 1
           do 10 i = 1, length
               result_vec(j) = start_vec(k) - sub_vec(l)
               j = j + inc3
               k = k + inc1
               l = l + inc2
       10  continue

     start_vec
          The vector to subtract sub_vec from.

     inc1 An increment for the index of start_vec that chooses which elements
          the elements of sub_vec will be subtracted from.

     sub_vec
          The vector to subtract from start_vec.

     inc2 An increment for the index of sub_vec that chooses which elements
          will be subtracted from the elements of start_vec.

     length
          The number of scalar differences to calculate.

     result_vec
          The difference of start_vec and sub_vec.

     inc3 An increment for the index of result_vec that chooses which elements
          will received the differences.

NOTES
     In C and Pascal, vec_$sub_i operates on column vectors; whereas in FOR-
     TRAN, it operates on row vectors.

SEE ALSO
     vec_$dsub_i, vec_$isub16_i, vec_$isub_i, vec_$sub.