R Under development (unstable) (2024-07-15 r86902 ucrt) -- "Unsuffered Consequences"
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Platform: x86_64-w64-mingw32/x64

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> library(s2)
> 
> u = s2_union(
+    "POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))",
+    "POLYGON ((5 5, 15 5, 15 15, 5 15, 5 5))",
+    s2_options(snap = s2_snap_level(30))
+ )
> s2_area(u, radius = 1)
[1] 0.05284581
> s2_area("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))", radius = 1) +
+ s2_area("POLYGON ((5 5, 15 5, 15 15, 5 15, 5 5))", radius = 1) -
+ s2_area("POLYGON ((5 5, 10 5, 10 15, 5 10, 5 5))", radius = 1)
[1] 0.04910511
> s2_area("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))", radius = 1)
[1] 0.03038216
> s2_area("POLYGON ((5 5, 15 5, 15 15, 5 15, 5 5))", radius = 1)
[1] 0.03002974
> s2_area("POLYGON ((5 5, 10 5, 10 15, 5 10, 5 5))", radius = 1)
[1] 0.01130679
> 
> df = s2_difference(
+    "POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))",
+    "POLYGON ((5 5, 15 5, 15 15, 5 15, 5 5))",
+    s2_options(snap = s2_snap_level(30))
+ )
> s2_area(df, radius = 1) -
+   (s2_area("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))", radius = 1) -
+     s2_area("POLYGON ((5 5, 10 5, 10 15, 5 10, 5 5))", radius = 1))
[1] 0.003740703
> 
> proc.time()
   user  system elapsed 
   0.26    0.06    0.31