Re: [proto] Using a derived class as terminals in Boost.proto

[Eric Niebler]

Proto grammars and transforms handle this better than evaluators, which are
deprecated. It would pay to look into some examples that use transforms.
Sorry, that's all the advice I have time for at the moment.

\e
On Apr 14, 2016 10:33 AM, "Mathias Gaunard" 
wrote:

> I'd try to use IsVector.
> I'm not sure how to do this with a grammar (maybe someone can pitch in)
> but you could do something like this
>
> enable_if< IsVector::type> >
>
> On 14 April 2016 at 18:04, Frank Winter  wrote:
>
>> I made some progress. If I specialize struct VectorSubscriptCtx::eval
>> with Vector10, like
>>
>>
>> struct VectorSubscriptCtx
>> {
>> VectorSubscriptCtx(std::size_t i) : i_(i) {}
>>
>> template
>> struct eval
>> : proto::default_eval
>> {};
>>
>> template
>> struct eval<
>> Expr
>> , typename boost::enable_if<
>> proto::matches >
>> >::type
>> >
>> {
>> //..
>> }
>> };
>>
>> then it works (is was specialized with Vector). It also works when using
>> the Boost _ literal (match anything), like
>>
>> template
>> struct eval<
>> Expr
>> , typename boost::enable_if<
>> proto::matches >
>> >::type
>>
>>
>> However, I feel this is not good style. Can this be expressed with the
>> is_base_of trait instead?
>>
>>
>>
>>
>>
>> On 04/14/2016 10:10 AM, Mathias Gaunard wrote:
>>
>>> On 14 April 2016 at 14:43, Frank Winter >> > wrote:
>>>
>>> Hi all!
>>>
>>> Suppose you'd want to implement a simple EDSL (Embedded Domain
>>> Specific Language) with Boost.proto with the following requirements:
>>>
>>>  Custom class 'Vector' as terminal
>>>  Classes derived from 'Vector' are working terminals too, e.g.
>>> Vector10
>>>
>>> [...]
>>>
>>> template
>>> struct IsVector
>>>: mpl::false_
>>> {};
>>>
>>>
>>> template<>
>>> struct IsVector< Vector >
>>>: mpl::true_
>>> {};
>>>
>>>
>>> Surely this should be true for all types derived from Vector.
>>>
>>> template
>>> struct IsVector
>>>: mpl::false_
>>> {};
>>>
>>> template
>>> struct IsVector >::type>
>>>: mpl::true_
>>> {};
>>>
>>>
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>
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Re: [proto] Using a derived class as terminals in Boost.proto

[Mathias Gaunard]

On 14 April 2016 at 15:37, Frank Winter  wrote:

>
> and still, I get basically the same error message:
>
> /home/fwinter/src/boost_1_60_0/boost/proto/context/default.hpp:121:41:
> error: no match for ‘operator+’ (operand types are ‘Vector10’ and
> ‘Vector10’)
>  BOOST_PROTO_BINARY_DEFAULT_EVAL(+, proto::tag::plus, make, make)
>
>
> It's weird since the operator+ should be there for Vector, and since I am
> importing the namespace VectorOps, it should work for derived classes. I
> don't see why it's not working.


A recent enough compiler should tell you which candidates it tried and why
they were removed due to SFINAE.
I don't have the time to try out your code at the moment but I recommend
you try to take a look at this.
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Re: [proto] Using a derived class as terminals in Boost.proto

[Frank Winter]

On 04/14/2016 10:10 AM, Mathias Gaunard wrote:

On 14 April 2016 at 14:43, Frank Winter > wrote:

Hi all!

Suppose you'd want to implement a simple EDSL (Embedded Domain
Specific Language) with Boost.proto with the following requirements:

 Custom class 'Vector' as terminal
 Classes derived from 'Vector' are working terminals too, e.g.
Vector10

[...]

template
struct IsVector
   : mpl::false_
{};


template<>
struct IsVector< Vector >
   : mpl::true_
{};


Surely this should be true for all types derived from Vector.

template
struct IsVector
   : mpl::false_
{};

template
struct IsVector >::type>
   : mpl::true_
{};




I had tried this


template<>
struct IsVector< Vector10 >
  : mpl::true_
{};


before. Same error message. Now I tried the base_of implementation


template
struct IsVector
  : mpl::false_
{};

template
struct IsVectorT>::value >::type>

  : mpl::true_
{};


and still, I get basically the same error message:

/home/fwinter/src/boost_1_60_0/boost/proto/context/default.hpp:121:41: 
error: no match for ‘operator+’ (operand types are ‘Vector10’ and 
‘Vector10’)

 BOOST_PROTO_BINARY_DEFAULT_EVAL(+, proto::tag::plus, make, make)


It's weird since the operator+ should be there for Vector, and since I 
am importing the namespace VectorOps, it should work for derived 
classes. I don't see why it's not working.


Thanks,
Frank




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Re: [proto] Using a derived class as terminals in Boost.proto

[Mathias Gaunard]

On 14 April 2016 at 14:43, Frank Winter  wrote:

> Hi all!
>
> Suppose you'd want to implement a simple EDSL (Embedded Domain Specific
> Language) with Boost.proto with the following requirements:
>
> Custom class 'Vector' as terminal
> Classes derived from 'Vector' are working terminals too, e.g. Vector10
>
> [...]

template
> struct IsVector
>   : mpl::false_
> {};
>
>
> template<>
> struct IsVector< Vector >
>   : mpl::true_
> {};
>
>
Surely this should be true for all types derived from Vector.

template
struct IsVector
  : mpl::false_
{};

template
struct IsVector >::type>
  : mpl::true_
{};
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Re: [proto] Using a derived class as terminals in Boost.proto

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