SUBROUTINE PPQAD(LDC,C,XI,LXI,K,X1,X2,PQUAD)
C***BEGIN PROLOGUE  PPQAD
C***DATE WRITTEN   800901   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  H2A2A1,E3,K6
C***KEYWORDS  B-SPLINE,DATA FITTING,INTERPOLATION,QUADRATURE,SPLINE
C***AUTHOR  AMOS, D. E., (SNLA)
C***PURPOSE  Computes the integral on (X1,X2) of a K-th order B-spline
C            using the piecewise polynomial representation.
C***DESCRIPTION
C
C     Written by D. E. Amos, June, 1979.
C
C     Reference SAND-79-1825
C
C     Abstract
C         PPQAD computes the integral on (X1,X2) of a K-th order
C         B-spline using the piecewise polynomial representation
C         (C,XI,LXI,K).  Here the Taylor expansion about the left
C         end point XI(J) of the J-th interval is integrated and
C         evaluated on subintervals of (X1,X2) which are formed by
C         included break points.  Integration outside (XI(1),XI(LXI+1))
C         is permitted.
C
C         PPQAD calls INTRV
C
C     Description of Arguments
C         Input
C           LDC    - leading dimension of matrix C, LDC .GE. K
C           C(I,J) - right Taylor derivatives at XI(J), I=1,K , J=1,LXI
C           XI(*)  - break point array of length LXI+1
C           LXI    - number of polynomial pieces
C           K      - order of B-spline, K .GE. 1
C           X1,X2  - end points of quadrature interval, normally in
C                    XI(1) .LE. X .LE. XI(LXI+1)
C
C         Output
C           PQUAD  - integral of the PP representation over (X1,X2)
C
C     Error Conditions
C         Improper input is a fatal error
C***REFERENCES  D.E. AMOS, *QUADRATURE SUBROUTINES FOR SPLINES AND
C                 B-SPLINES*, SAND79-1825, SANDIA LABORATORIES,
C                 DECEMBER 1979.
C***ROUTINES CALLED  INTRV,XERROR
C***END PROLOGUE  PPQAD