ccc-----------------------------------------------/fpintrp
ccc	linear interpolation
ccc
	real function fpintrp(x,fa,xa,n)
c
c returns fpintrp= f(x)
c fa(i) = f(xa(i))	set of n known values of x and f(x).
c xa	is assumed to be ordered from smallest to largest
c
c if the xa array is equally spaced, then the faster finteq1d routine
c can be used.  Note that this routine does zero extrapolation beyond
c the endpoints of xa, while finteq1d does do extrapolation...
c
	real fa(n),xa(n)
 
20	j=lkupr(x,xa,n)+1

	if(j .eq. 1) then
	    fpintrp=fa(1)    !default for x<xa(1)
	    return
	endif

	if(j .gt. n)then
	    fpintrp=fa(n)    !default for x>xa(n)
	    return
	endif
 
50	fpintrp=( fa(j-1)*(xa(j)-x) + fa(j)*(x-xa(j-1)) )
	1	 / (xa(j)-xa(j-1))
 
	return
	end