They would have for constraint

  `if (isInputRange!Range && isInputRange!(ElementType!Range))`

In case you wouldn't see directly what would they be used for, it's for tree-like structures. Each element in a Range is also an input range.

I see 3 obvious functions/templates

- the most important, make an input range from a tree-like range, e.g `auto treeRange(Range, DepthMode mode)(Range range) `

- a second version for bidir ranges, e.g `reverseTreeRange`

- a functional iteration algorithm: auto `deepIterate(alias Fun, DepthMode mode, Range, A...)(Range range, auto ref A a)`, which applies Fun to each element with the ability for Fun to act as a predicates to stop the iteration. Actually I have this one in my user library (this is also the reason why I post this today).

Unless I'm blind I cannot see anything that handles trees with a range interface in phobos.

On Friday, 21 October 2016 at 19:41:00 UTC, Basile B. wrote:
> They would have for constraint
>
>   `if (isInputRange!Range && isInputRange!(ElementType!Range))`
>
> In case you wouldn't see directly what would they be used for, it's for tree-like structures. Each element in a Range is also an input range.
>
> I see 3 obvious functions/templates
>
> - the most important, make an input range from a tree-like range, e.g `auto treeRange(Range, DepthMode mode)(Range range) `
>
> - a second version for bidir ranges, e.g `reverseTreeRange`
>
> - a functional iteration algorithm: auto `deepIterate(alias Fun, DepthMode mode, Range, A...)(Range range, auto ref A a)`, which applies Fun to each element with the ability for Fun to act as a predicates to stop the iteration. Actually I have this one in my user library (this is also the reason why I post this today).
>
> Unless I'm blind I cannot see anything that handles trees with a range interface in phobos.

If you want to get the spirit see: https://github.com/BBasile/iz/blob/master/import/iz/sugar.d#L1214

Now a few hours later I wonder if it could be a ndSlice job ? I haven't used it so far, so I ask.