CDECK  ID>, HWRPOW.

*CMZ :-        -26/04/91  11.11.56  by  Bryan Webber

*-- Author :    Bryan Webber

C-----------------------------------------------------------------------

      SUBROUTINE HWRPOW(XVAL,XJAC)

C-----------------------------------------------------------------------

C     RETURNS XVAL DISTRIBUTED ON (XMIN,XMAX) LIKE XVAL**XPOW

C     AND CORRESPONDING JACOBIAN FACTOR XJAC

C     SET FIRST=.TRUE. IF NEW XMIN,XMAX OR XPOW

C-----------------------------------------------------------------------

      DOUBLE PRECISION HWR,XVAL,XJAC,XMIN,XMAX,XPOW,P,Q,A,B,C,Z,ZERO

      LOGICAL FIRST

      PARAMETER(ZERO=0.0D0)

      EXTERNAL HWR

      SAVE Q,A,B,C

      COMMON/HWRPIN/XMIN,XMAX,XPOW,FIRST

      IF (FIRST) THEN

        P=XPOW+1.

        IF (P.EQ.ZERO) CALL HWWARN('HWRPOW',500,*999)

        Q=1./P

        A=XMIN**P

        B=XMAX**P-A

        C=B*Q

        FIRST=.FALSE.

      ENDIF

      Z=A+B*HWR()

      XVAL=Z**Q

      XJAC=XVAL*C/Z

  999 END

CDECK  ID>, HWRUNG.

*CMZ :-        -26/04/91  14.55.45  by  Federico Carminati

*-- Author :    David Ward, modified by Bryan Webber

C-----------------------------------------------------------------------

      FUNCTION HWRUNG(A,B)

C-----------------------------------------------------------------------

C     Random number from distribution having flat top [-A,A] & gaussian

C     tail of s.d. B

C-----------------------------------------------------------------------

      DOUBLE PRECISION HWRUNG,HWRGAU,HWRUNI,A,B,PRUN,ZERO

      LOGICAL HWRLOG

      EXTERNAL HWRGAU,HWRUNI,HWRLOG

      PARAMETER (ZERO=0.D0)

      IF (A.EQ.ZERO) THEN

        PRUN=0

      ELSE

        PRUN=1./(1.+B*1.2533/A)

      ENDIF

      IF(HWRLOG(PRUN)) THEN

        HWRUNG=HWRUNI(0,-A,A)

      ELSE

        HWRUNG=HWRGAU(0,ZERO,B)

        HWRUNG=HWRUNG+SIGN(A,HWRUNG)

      ENDIF

      END