Re: [Boost-users] [Boost.Assign] list_of::range without an initial (single) element?

Michael McNeil Forbes skrev:

Thorsten Ottosen wrote:

...

Just to be clear, you want list_of() to be empty_list_of<*any type*>(), and for the type of the list to be deduced by the first argument:

list_of()(42);

would be a list of ints with one value (42).

This is what I was expecting when I first started. Semantically this behaviour seems to make sense, but I have not thought too deeply about it.

...

If so, I think this syntax is possible, but I am worried that the difference between list_of() and list_of<T>() is too subtle.

What exactly would be the subtle difference between these two? Would they not both be forms of empty lists, except the second form would only accept arguments of type T?

Currently list_of<int>() is not an empty list.

The other thing I was expecting was perhaps an exposed range() function so that one can just go:

... = range(a).range(b)

(I also thought that the exposed repeat() functions would also allow for this:

boost::array c = boost::assign::repeat(4, 5);

use but I apparently do not understand yet how the exposed repeat is intended to be used.)

array has a fill member for that purpose, albeit it lacks a constructor. No, repeat() and range() are used inside lists: push_back( vec ) += 1,2,3,repeat(4,5),range(other_rng),5,6,7;

I have to look more deeply into the new proposal for operator&&(), but it seems a little specific. Is there no way that the ideas discussed here could be made as efficient, requiring a separate operator&&() for chaining? As a user, I would not mind being steered towards the efficient usage if documented properly.

The new methods are quite efficient. In the old library, list_of<T>() is not efficient (ease of use is the key goal here), whereas ref_list_of<T>()/cref_list_of() are. -Thorsten -Thorsten