• Freddy (2/2) Oct 02 2015 How do I use http://dlang.org/phobos/std_range_interfaces.html in
• Jonathan M Davis via Digitalmars-d-learn (24/26) Oct 03 2015 You don't. None of the functions in those interfaces are marked with @sa...

Freddy <Hexagonalstar64 gmail.com> writes:

How do I use http://dlang.org/phobos/std_range_interfaces.html in 
pure  safe code?

Jonathan M Davis via Digitalmars-d-learn writes:

On Friday, October 02, 2015 19:45:05 Freddy via Digitalmars-d-learn wrote:
 How do I use http://dlang.org/phobos/std_range_interfaces.html in
 pure  safe code?

You don't. None of the functions in those interfaces are marked with  safe
or pure. One of the problems with classes is that you're stuck with whatever
attributes a base class put on a function. If it has an attribute like  safe
or pure, then the derived class can't do anything that requires that they
be  system or pure, whereas if it doesn't have those attributes, then it
can't be used in code that's  safe or pure. For  safe,  trusted can be used,
but that only makes sense if the the code is legitimately  safe in spite of
the  system stuff that it's doing (i.e. the programmer verified it), whereas
if it depends on the caller or just plain isn't  safe, then you're stuck,
and with pure, you're pretty much just stuck. nothrow has the same problems.

In general, I would strongly advise against using any of the interfaces in
std.range.interfaces and just use structs and templatize your code. Then you
don't run into any of those problems, since pure,  safe, and nothrow get
inferred as appropriate, and it's likely to be more efficient, since you
don't end up with any virtual calls, and there are better optimization
opportunities (such as inlining).

But if you do really need to use interfaces like that, then you can just
write your own and put whatever attributes you want on their functions. That
won't work if you have to interact with someone else's code that's using
those interfaces, but aside from that, it should work just fine.

But if you _have_ to use those interfaces, then you simply can't use them in
code that has to be  safe, pure, or nothrow.

- Jonathan M Davis