As a follow-up question to

http://forum.dlang.org/thread/jkbhlezbcrufowxtthmy@forum.dlang.org?page=3#post-zyuqclyjitbhavemmwto:40forum.dlang.org

discussing the motivation for a new range primitive stealFront that combines moveFront and popFront implemented at

https://github.com/nordlow/justd/blob/master/range_ex.d#L14

I then wonder if there's a way to check, using a type-trait, whether the value returned from moveFront is safe to use after popFront has been called on it. If so I want to restrict stealFront/Back with this trait.

On Saturday, 1 November 2014 at 21:26:49 UTC, Nordlöw wrote:
> As a follow-up question to
>
> http://forum.dlang.org/thread/jkbhlezbcrufowxtthmy@forum.dlang.org?page=3#post-zyuqclyjitbhavemmwto:40forum.dlang.org
>
> discussing the motivation for a new range primitive stealFront that combines moveFront and popFront implemented at
>
> https://github.com/nordlow/justd/blob/master/range_ex.d#L14
>
> I then wonder if there's a way to check, using a type-trait, whether the value returned from moveFront is safe to use after popFront has been called on it. If so I want to restrict stealFront/Back with this trait.

Not currently, but see my proposal:
http://wiki.dlang.org/User:Schuetzm/scope#scope.21.28const_....29

On Sunday, 2 November 2014 at 11:55:41 UTC, Marc Schütz wrote:
> On Saturday, 1 November 2014 at 21:26:49 UTC, Nordlöw wrote:
>> As a follow-up question to
>>
>> http://forum.dlang.org/thread/jkbhlezbcrufowxtthmy@forum.dlang.org?page=3#post-zyuqclyjitbhavemmwto:40forum.dlang.org
>>
>> discussing the motivation for a new range primitive stealFront that combines moveFront and popFront implemented at
>>
>> https://github.com/nordlow/justd/blob/master/range_ex.d#L14
>>
>> I then wonder if there's a way to check, using a type-trait, whether the value returned from moveFront is safe to use after popFront has been called on it. If so I want to restrict stealFront/Back with this trait.
>
> Not currently, but see my proposal:
> http://wiki.dlang.org/User:Schuetzm/scope#scope.21.28const_....29

Thanks. A trivial solution, but probably too great restriction, would be

auto stealFront(R)(ref R r) if (!hasIndirections!(ElementType!R))

a smaller restriction would be to use

auto stealFront(R)(ref R r) if (!hasUnsharedAliasing!(ElementType!R))

Can hasUnsharedAliasing be used in my case?

For detail see

- http://dlang.org/phobos/std_traits.html#hasIndirections
- http://dlang.org/phobos/std_traits.html#hasUnsharedAliasing

On Saturday, 1 November 2014 at 21:26:49 UTC, Nordlöw wrote:
> https://github.com/nordlow/justd/blob/master/range_ex.d#L14

Moved here

https://github.com/nordlow/phobos-next/blob/master/src/range_ex.d#L66