[Python-Dev] Return type of round, floor, and ceil in 2.6

[glyph at divmod.com]

On 4 Jan, 10:45 pm, python at rcn.com wrote:
>[GvR to Tim]
>>Do you have an opinion as to whether we should
>>adopt round-to-even at all (as a default)?
>
>For the sake of other implementations (Jython, etc) and for ease of 
>reproducing the results with other tools (Excel, etc), the simplest 
>choice is int(x+0.5).  That works everywhere, it is easy to explain, it 
>runs fast, and it is not hard to get right.

I agree for the default.  Except the part where Excel, Jython, and 
Python's current round, actually use sign(x) * int(abs(x)+0.5), so maybe 
it's not *completely* easy to get right ;-).

Having other rounding methods *available*, though, would be neat.  The 
only application I've ever worked on where I cared about the difference, 
the user had to select it (since accounting requirements differ by 
jurisdiction and, apparently, by bank preference).  Having a standard 
way to express this (especially if it worked across different numeric 
types, but perhaps I digress) would be pleasant.  Implementing 
stochastic rounding and banker's rounding oneself, while not exactly 
hard, is a drag.