Re: [Boost-users] [units] Dimensionless? expecting length+length

Subject: Re: [Boost-users] [units] Dimensionless? expecting length+length
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2015-08-10 22:50:36

On 11/08/2015 14:12, Michael wrote:
>> You can, but it's not necessary.  Simply assign value * milli * seconds
>>
>> to a variable of quantity<time> (aka Time) and it automatically
>> converts
>> everything to seconds (since that's the base unit of "time").  This
>> prevents other operations getting confused by scaled units, which
>> happens when you use "auto" because it skips this conversion.
>
> Ah I gotcha. So the prevailing wisdom is auto auto auto, except when
> quantities and prefixed unit conversions are concerned.

I'm not sure about "prevailing wisdom".  I don't use auto anywhere with 
Boost.Units (I use explicit types as mentioned above instead).  But 
then, most of my usage of Boost.Units was written in the dark ages 
(C++03 compiler).

TBH your code seems a little too auto-happy to me -- I wouldn't have 
defined things like "two" or "milliseconds" or "gValue" or the 
static_casts and would have just written the values inline instead, as I 
think it's sufficiently clear that way.  But that's just a coding style 
thing (the compiler should be smart enough to generate the same code 
either way) and if you think that makes it clearer for you then go for 
it.  That's probably a more reasonable place to use "auto", for things 
that aren't quantities.