PERF: RangeIndex.is_monotonic_inc/dec - #13749

Maybe add a test for the empty case as well?

In [23]: pd.RangeIndex().is_monotonic_increasing
Out[23]: True

In [24]: pd.RangeIndex().is_monotonic_decreasing
Out[24]: True

Although this should maybe rather raise an error (@jreback)

Other index types to raise without arguments, and range() does as well.

@jorisvandenbossche empty case is coverd by (1, 1).

pd.RangeIndex(1, 1).values
# array([], dtype=int64)

Let me issue a separate PR to prohibit empty construction.

Ah yes, assumed that RangeIndex() does not has a step yet, but that is of course wrong :-)

yeah I don't think RangeIndex() should be permitted, though I seem to remember needing it for unpickling or somesuch.......

let's make a new issue about the empty RangeIndex()