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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
# ARCZ -- Vector reciprocal 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 arczr (a, b, c, npix, errfcn)
real a # numerator
real b[ARB], c[ARB] # divisor, and output arrays
int npix # number of pixels
real errfcn() # user function, called on divide by zero
int i
real divisor
real tol
extern errfcn()
errchk errfcn
begin
if (a == 0.0) {
call aclrr (c, npix)
return
}
tol = 1.0E-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)
next
}
c[i] = a / divisor
}
end
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