Re: [boost] [type_traits] extension has_operator_xxx - conforming to coding guidelines for ICE

Subject: Re: [boost] [type_traits] extension has_operator_xxx - conforming to coding guidelines for ICE
From: Vicente Botet (vicente.botet_at_[hidden])
Date: 2011-02-03 18:02:55

Frédéric Bron wrote:
> 
>> Don't use dependent default parameters for non-type template parameters.
>> For example:
>>
>> template <class T, int I = ::boost::is_integral<T>::value>  // Error
>> can't deduce value of I in some cases.
>> struct foobar;
>>
>> Rationale: this kind of usage fails for Borland C++. Note that this is
>> only an issue where the default value is dependent upon a previous
>> template parameter, for example the following is fine:
> 
> Is there any known workaround for this? In my case, int is replaced by
> bool but I think it is the same issue.
> 
> 

Hi, 

you could try to add an indirection.

template <class T, bool B> 
struct foobar_aux;

template <class T> 
struct foobar : foobar_aux<T, ::boost::is_integral<T>::value> {};

HTH,
Vicente
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