c
c
c
c =================================================
function fdisc(x,y)
c =================================================
implicit double precision (a-h,o-z)
c
include "cuser.i"
c
c # for computing cell averages for initial data that has a
c # discontinuity along some curve. fdisc should be negative to the
c # left of the curve and positive to the right
c # idisc specifies the nature of the discontinuity for two
c # particular cases (a straight line and circle) but this routine
c # can be modified for any other curve.
c
c # circle of radius r0
alpha = datan(y/x)
radi = ri - ai*dcos(aw*alpha)
fdisc = (x-x0)**2 + (y-y0)**2 - radi**2
c
return
end