Subject: Re: [boost] GDB-like debugger for template metaprograms
From: Larry Evans (cppljevans_at_[hidden])
Date: 2014-11-29 17:57:02
On 11/29/2014 04:06 PM, Mathias Gaunard wrote:
> On 29/11/2014 22:15, Abel Sinkovics wrote:
>> Hi Mathias,
>>
>> Thank you for checking it.
>>
>> On 2014-11-29 18:56, Mathias Gaunard wrote:
>>> - pretty printing complex types so that you can actually read them
>>> I don't think the formatter thing is a solution.
>>> Consider an arbitrarily deep expression template tree, for example.
>> We have some ideas on how to improve pretty printing of types and
>> displaying complex template instances based on our own experience.
>>
>> How would you change/improve pretty printing in a way you find useful?
>> How would you display for example a deep expression template tree?
>
> It can be hard to match '<' and '>' together for long symbol names
> involving instantiations of templates where the parameters are
> themselves template instantiations.
>
> I think it would be great to have an option to automatically indent the
> type when printing so that it's easier to interpret.
>
> Instead of
> a<b,c<d>,e<f<g,h>>,i>, you could print it as
>
> a<
> b,
> c<d>,
> e<
> f<g, h>
> >,
> i
>>
Or, keep *all* the delimiters(< , and >)
lined up, as in the following
( where the delimiters are lined up only
for the expr_prefx template):
expr_prefx
< op_ator< []>
, expr_prefx
< op_symb<lit,lit1>
>
, expr_prefx
< op_symb<act,action1>
>
>
This output was produced by:
template
< typename Operator
, typename... Operands
>
friend
std::ostream&
operator<<
( std::ostream& os
, expr_prefx
< Operator
, Operands...
>
)
{
os
<<"expr_prefx\n< "
<<indent_buf_in<<Operator{};
using swallow = int[]; // guaranties left to right order
(void)swallow
{ 0
, ( os
<<"\n"
<<indent_buf_out
<<", "
<<indent_buf_in<<Operands{}
, 0
)...
};
os<<indent_buf_out<<"\n>";
return os;
}
the indent_buf_in is an io manipulator that uses boost::iostreams
and an iostreams indent filter, which I can provide.
HTH.
-regards,
Larry