From: boost-users-bounces@lists.boost.org
[mailto:boost-users-bounces@lists.boost.org] On Behalf Of Murilo Adriano
Vasconcelos
Sent: Wednesday, July 14, 2010 9:04 PM
To: boost-users@lists.boost.org
Subject: [Boost-users] About naming of integer log in base 2
Hi all,
I implemented a function [0] wich computes the logarithm in
base two of integers and want to know what naming is most appropriated:
ilog2
or simply
log2
My instinct is for log2 so it might be specialised for floating
point too.
Glancing at your code, I note you don’t explicitly check that
type T is integer (but perhaps is_signed does that?)
But I feel that * If `value` is equal to 0, the value returned is undefined
may be evil in some peoples opinion.
Of course it is always a vexed question what to do for the
corner cases like this. I am sure that this sort of issue will raise its
ugly head for other functions.
You might like to consider making problem cases ‘policy controlled’.
In the Boost.Math package John Maddock went to the trouble of
providing a way of letting users controlling what happens for cases like this.
(He retrofitted policies, so you don’t have to do it
immediately – but doing it will focus your mind on the possible corner
cases).
If you read the math docs, perhaps the pdf at
http://boost.cowic.de/rc/pdf/math.pdf
or the download from source,
and see the section on Policies you will see what it being
suggested, and some examples.
You might return zero, or ? or throw an exception?
You can consult and see if there is a consensus on the default
policy.
At least it may reduce the discussion (Boosters are really good
at that ;-) on what *should* happen, if you can say “You *can*
make it do what you want.”
Paul
---
Paul A. Bristow
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Kendal, UK LA8 8AB
+44 1539 561830, mobile +44 7714330204
pbristow@hetp.u-net.com