[Dune-devel] [Dune-Commit] [Commit] dune-geometry - cb66db8: Add explicit conversion, needed when using high precision types like boost::multiprecision

[Martin Nolte]

Hi Andreas,

so Christian is perfectly correct in assuming that the cast ctype( df / cxn ) is 
not nessassary. However, the basic problem might persist with expression 
templates as, e.g., (b > ctype( 1 ) ? a / b : a * b) may result in a compiler error.

But, as I said, we should discuss this on the developer meeting.

Best,

Martin

On 06/13/2014 02:05 PM, Andreas Buhr wrote:
> Hi Martin,
>
> On 06/13/2014 01:28 PM, Martin Nolte wrote:
>> Your compiler output
>> indicates that you have not tested the option
>>
>> ctype dfcxn = (cxn > Traits::tolerance() || cxn < -Traits::tolerance())
>> ? df / cxn : ctype(0);
>>
>> Does the compiler accept that?
>
> The compiler accepts both:
> ... ? df / cxn : ctype(0);
> and
> ... ? ctype(df / cxn) : 0;
>
> The reason is that, according to § 5.3 paragraph 3 in the C++ standard
> (draft):
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3337.pdf
>
> <cite>
> ... if the second and third operand have different types and either has
> (possibly cv-qualified) class type, or if both are glvalues of the same
> value category and the same type except for cv-qualification, an attempt
> is made to convert each of those operands to the type of the other.
> </cite>
>
> cheers,
> Andreas
>
>
>
>
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-- 
Dr. Martin Nolte <nolte at mathematik.uni-freiburg.de>

Universität Freiburg                                   phone: +49-761-203-5630
Abteilung für angewandte Mathematik                    fax:   +49-761-203-5632
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79104 Freiburg, Germany