Function S2CellId.rangeMin
These methods return the range of cell ids that are contained within this cell \(including itself\).
The range is *inclusive* \(i.e. test using >= and <=\) and the return values of both methods
are valid leaf cell ids. In other words, a if and only if
(b >= a If you want to iterate through all the descendants of this cell at a
particular level, use childBegin(level) and childEnd(level) instead.
Also see maximumTile(), which can be used to iterate through a range of
cells using S2CellIds at different levels that are as large as possible.
If you need to convert the range to a semi-open interval \[min, limit\)
\(e.g., in order to use a key-value store that only supports semi-open
range queries\), do not attempt to define "limit" as range_max.
The problem is that leaf S2CellIds are 2 units apart, so the semi-open
interval \[min, limit\) includes an additional value (range_max
which is happens to be a valid S2CellId about one-third of the time and
is *never* contained by this cell. \(It always correpsonds to a cell that
is larger than this one.\) You can define "limit" as (range_max
if necessary \(which is not always a valid S2CellId but can still be used
with FromToken/ToToken\), or you can convert rangeMax() to the key space
of your key-value store and define "limit" as successor(key).
Note that Sentinel().