edponce commented on a change in pull request #10349:
URL: https://github.com/apache/arrow/pull/10349#discussion_r659957016
##########
File path: docs/source/cpp/compute.rst
##########
@@ -312,6 +313,79 @@ precision of `divide` is at least the sum of precisions of
both operands with
enough scale kept. Error is returned if the result precision is beyond the
decimal value range.
+Rounding functions
+~~~~~~~~~~~~~~~~~~
+
+These functions displace numeric input(s) to approximate and shorter numeric
+representation(s). Integral input(s) produce floating-point output(s) of same
value.
+If any of the input element(s) is null, the corresponding output element is
null.
+
++---------------+------------+-------------+-------------+----------------------------------+
+| Function name | Arity | Input types | Output type | Notes | Options
class |
++===============+============+=============+=============+==================================+
+| mround | Unary | Numeric | Float32/64 | (1)(2) |
:struct:`MRoundOptions` |
++---------------+------------+-------------+-------------+----------------------------------+
+| round | Unary | Numeric | Float32/64 | (1)(3) |
:struct:`RoundOptions` |
++---------------+------------+-------------+-------------+----------------------------------+
+
+* \(1) Output value is a 64-bit floating-point for integral inputs and the
+ retains the same type for floating-point inputs. By default rounding
functions
+ displace a value to the nearest integer with a round to even for breaking
ties.
+ Options are available to control the rounding behavior.
+* \(2) The ``multiple`` option specifies the rounding
+ scale and precision. Only the magnitude of the ``rounding multiple`` is
used,
+ its sign is ignored.
+* \(3) The ``ndigits`` option specifies the rounding precision in
+ terms of number of digits. A negative value corresponds to digits in the
+ non-decimal part.
+
++-------------------------+---------------------------------+
+| Round mode | Description/Examples |
++=========================+=================================+
+| DOWNWARD | Equivalent to ``floor(x)`` |
+| TOWARDS_NEG_INFINITY | 3.7 = 3, -3.2 = -4 |
Review comment:
Agree, good observation.
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