[boost] Re: N-arity operators in C++, also reducing temporaries. [Repost]

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2005-03-09 04:46:50

Larry Evans wrote:
> On 03/08/2005 06:26 AM, Tobias Schwinger wrote:
> [snip]
> 
>> I use 'apply', 'apply_one' and 'apply_but' functions that allow me to 
>> apply functors to all elements, one element and all but one elements, 
>> respectively (I use different versions for both static and dynamic 
>> indices and both static and dynamic functors):
> 
> 
> What does "static" and "dynamic" mean here?  Does static mean
> "evaluable at compile time" and "dynamic" means otherwise?
> 

Yes. A curious question: what else could it possibly mean in this context ?

> [snip]
> 
>> - Do you know the Boost.Assign technique ?
>> I use a similar approach to have a nice syntax for initialization and 
>> inlining that works within expressions:
>>
>>   my_quaternion = n_x * sin_half_a
>>                 , n_y * sin_half_a
>>                 , n_z * sin_half_a
>>                 , cos_half_a;
>>
>> and
>>
>>   vector_slice<0,3> (my_quaternion)
>>     = (vec_inl| n_x,n_y,0.0) * sin_half_a;
>>
> Never seen this (vec_inl| n_x,n_y,0.0).  Looks like
> a set expression or lambda expression.  Could you
> provide a reference.  I searched:
> 
> http://www.boost.org/libs/assign/doc/index.html#reference
> 
> for the character '|' but got no results.

This is _not_ Boost.Assign! As stated above it's part of my private 
library but it has some similarities to Boost.Assign.

I use this to allow per-element data to be inlined in expressions.
'operator|' is overloaded for a tag type (vec_inl is a global of that 
type) and scalar types, creates an expression object for which an 
overloaded 'operator,' exists to append elements.

>>
>>
>> ( The 'my_quaternion' variable from the examples is a four-dimensional 
>> vector, _not_ a boost::quaternion. )
>>
> Does "four-dimensional" mean "length is four" or "accessing a scalar
> requires four indices passed to the operator()", e.g.

Is this really that ambiguous ? AFAIK it's a proper mathematical term...
Besides quaternions consist of four scalars (so I might as well omitted 
'four-dimensional'). I found it necessary to disclaim it's not a 
boost::quaternion, though...

Regards,

Tobias