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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
# ADVZ -- Vector divide with checking for zero divisors. If the result of a
# divide would be undefined a user supplied function is called to get the
# output pixel value.
#
# NOTE: in the interests of simplicity a somewhat arbitrary tolerance is used
# to check for an undefined divide, i.e., a divide by zero or a divide by a
# number small enough to cause floating point overflow. A better way to do
# this would be to provide a machine dependent version of this operator in
# host$as which catches the hardware exception rather than using a comparison.
procedure advzd (a, b, c, npix, errfcn)
double a[ARB], b[ARB], c[ARB] # numerator, divisor, and output arrays
int npix # number of pixels
double errfcn() # user function, called on divide by zero
int i
double divisor
double tol
extern errfcn()
errchk errfcn
begin
tol = 1.0D-20
do i = 1, npix {
divisor = b[i]
# The following is most efficient when the data tends to be
# positive.
if (divisor < tol)
if (divisor > -tol) {
c[i] = errfcn (a[i])
next
}
c[i] = a[i] / divisor
}
end
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