*
* $Id: arstra.F,v 1.1.1.1 1996/03/08 16:51:05 mclareni Exp $
*
* $Log: arstra.F,v $
* Revision 1.1.1.1  1996/03/08 16:51:05  mclareni
* Ariadne
*
*
#include "ariadne/pilot.h"
C***********************************************************************
 
      REAL FUNCTION ARSTRA(KF,KQ,X,XP,XQ2)
 
C...ARiadne function Structure Function RAtio
 
C...Return ratio of structure functions for given flavour, x, xp and Q^2
 
      PARAMETER(MAXDIP=500,MAXPAR=500,MAXSTR=100)
 
      IMPLICIT DOUBLE PRECISION (D)
      IMPLICIT DOUBLE PRECISION (B)
      IMPLICIT LOGICAL (Q)
      COMMON /ARDAT1/ PARA(40),MSTA(40)
      SAVE /ARDAT1/
      COMMON /ARHIDE/ PHAR(400),MHAR(400)
      SAVE /ARHIDE/
 
      REAL XPQ(-6:6),XPYST(-25:25)
 
 
      IF (MSTA(1).EQ.3) THEN
        CALL LNSTRF(X/ABS(XP),XQ2,XPQ)
        ARSTRA=XPQ(0)
        CALL LNSTRF(X,XQ2,XPQ)
        XFQ=MIN(XPQ(KQ),XPQ(-KQ))
        IF (XP.LT.0.0.AND.PARA(19).LT.0.0) THEN
          IF (XFQ.LT.-PARA(19)) THEN
            ARSTRA=-1.0
            RETURN
          ENDIF
        ENDIF
C        IF (MHAR(118).EQ.0) XFQ=MAX(XFQ,ABS(PARA(19)))
        IF (MHAR(118).EQ.0.AND.XFQ.LT.ABS(PARA(19))) THEN
          XFQ=ABS(PARA(19))
        ENDIF
        IF (XFQ.GT.0.0) THEN
          ARSTRA=ARSTRA/XFQ
        ELSE
          ARSTRA=-1.0
        ENDIF
      ELSE
        CALL PYSTFU(KF,X/ABS(XP),XQ2,XPYST)
        ARSTRA=XPYST(0)
        CALL PYSTFU(KF,X,XQ2,XPYST)
        XFQ=MIN(XPYST(KQ),XPYST(-KQ))
        IF (XP.LT.0.0.AND.PARA(19).LT.0.0) THEN
          IF (XFQ.LT.-PARA(19)) THEN
            ARSTRA=-1.0
            RETURN
          ENDIF
        ENDIF
C        IF (MHAR(118).EQ.0) XFQ=MAX(XFQ,ABS(PARA(19)))
        IF (MHAR(118).EQ.0.AND.XFQ.LT.ABS(PARA(19))) THEN
          XFQ=ABS(PARA(19))
        ENDIF
        IF (XFQ.GT.0.0) THEN
          ARSTRA=ARSTRA/XFQ
        ELSE
          ARSTRA=-1.0
        ENDIF
      ENDIF
      IF (MHAR(102).NE.2) ARSTRA=ARSTRA*XP
 
      RETURN
 
C**** END OF ARSTRA ****************************************************
      END