[boost] Re: [string algo formal review]

From: David Abrahams (dave_at_[hidden])
Date: 2003-10-30 14:28:26

"Peter Dimov" <pdimov_at_[hidden]> writes:

> David Abrahams wrote:
>> "Thorsten Ottosen" <nesotto_at_[hidden]> writes:
>>
>>>> what it wrong with this and why do you want to use int instead?
>>>
>>> Basically I want to use int whereever posisble so I don't have to
>>> worry about signed to unsiged conversions. The fact that the
>>> standard library does so/allows just makes programming harder that
>>> it has to be.
>>
>> A tendency to use ints everywhere makes that a self-fulfilling
>> prophecy.  You can turn on warnings to catch the problems.  If
>> you're consistent about using unsigned for unsigned numbers, as
>> with const, you'll find that the actual cases where signed/unsigned
>> conversions need to be performed a much fewer.
>
> A rare case where I disagree with Dave. 

I don't think we're actually disagreeing.

> It is almost never necessary to use unsigned types in numeric
> contexts (as opposed to bit fiddling), and there are plenty of
> reasons to actively avoid them. For example, -1 / 4u or 1u
>> -1. 

Yep, those are the ones which good compilers can warn about, also.

> Unsigned types aren't "const correct" since the conversions are
> often silent and safe.

Optional warnings aside, that's right.  I was just saying that
consistent use of unsigned in the appropriate places often makes
signed/unsigned interactions rarer when you are forced to use them
anyway at std:: library interface boundaries.

Note that signed integers aren't exactly safe either.  Underflows and
overflows typically pass without notice, for example.  I always give
my C++ arithmetic two or three looks before I'm comfortable with it.
Maybe that's why signed/unsigned interactions don't worry me quite as
much as they do others.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com