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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <pkg/rg.h>
# RG_INTERSECT -- Intersect two sets of ordered and merged ranges.
pointer procedure rg_intersect (rg1, rg2)
pointer rg1 # First set of ranges
pointer rg2 # Second set of ranges
pointer rg3 # Pointer to intersection
int i, j, k
begin
# Error check the range pointers.
if ((rg1 == NULL) || (rg2 == NULL))
call error (0, "Range descriptor(s) undefined")
# Allocate the range points array.
k = RG_NRGS(rg1) + RG_NRGS(rg2) - 1
call malloc (rg3, LEN_RG + 2 * max (1, k), TY_STRUCT)
# Set the ranges.
i = 1
j = 1
k = 0
while (i <= RG_NRGS(rg1) && j <= RG_NRGS(rg2)) {
if (RG_X2(rg1, i) < RG_X1(rg2, j))
i = i + 1
else if (RG_X2(rg2, j) < RG_X1(rg1, i))
j = j + 1
else {
k = k + 1
RG_X1(rg3, k) = max (RG_X1(rg1, i), RG_X1(rg2, j))
RG_X2(rg3, k) = min (RG_X2(rg1, i), RG_X2(rg2, j))
if (RG_X2(rg1, i) < RG_X2(rg2, j))
i = i + 1
else
j = j + 1
}
}
call realloc (rg3, LEN_RG + 2 * max (1, k), TY_STRUCT)
RG_NRGS(rg3) = k
RG_NPTS(rg3) = 0
do i = 1, RG_NRGS(rg3)
RG_NPTS(rg3) = RG_NPTS(rg3) + RG_X2(rg3, i) - RG_X1(rg3, i) + 1
return (rg3)
end
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