SLATEC Routines --- DEFER ---

*DECK DEFER
      SUBROUTINE DEFER (COFX, COFY, IDMN, USOL, GRHS)
C***BEGIN PROLOGUE  DEFER
C***SUBSIDIARY
C***PURPOSE  Subsidiary to SEPELI
C***LIBRARY   SLATEC
C***TYPE      SINGLE PRECISION (DEFER-S)
C***AUTHOR  (UNKNOWN)
C***DESCRIPTION
C
C     This subroutine first approximates the truncation error given by
C     TRUN1(X,Y)=DLX**2*TX+DLY**2*TY where
C     TX=AFUN(X)*UXXXX/12.0+BFUN(X)*UXXX/6.0 on the interior and
C     at the boundaries if periodic (here UXXX,UXXXX are the third
C     and fourth partial derivatives of U with respect to X).
C     TX is of the form AFUN(X)/3.0*(UXXXX/4.0+UXXX/DLX)
C     at X=A or X=B if the boundary condition there is mixed.
C     TX=0.0 along specified boundaries.  TY has symmetric form
C     in Y with X,AFUN(X),BFUN(X) replaced by Y,DFUN(Y),EFUN(Y).
C     The second order solution in USOL is used to approximate
C     (via second order finite differencing) the truncation error
C     and the result is added to the right hand side in GRHS
C     and then transferred to USOL to be used as a new right
C     hand side when calling BLKTRI for a fourth order solution.
C
C***SEE ALSO  SEPELI
C***ROUTINES CALLED  DX, DY
C***COMMON BLOCKS    SPLPCM
C***REVISION HISTORY  (YYMMDD)
C   801001  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900402  Added TYPE section.  (WRB)
C***END PROLOGUE  DEFER