Itertools

[Ichthyostega]

Start a collection of Iterator-tools, similar to the Python module, or the Commons-Collections IteratorUtils, or the respective features of Groovy.

Of course we're not writing a library, so we'll add here what is needed, starting with

• a filtered iterator
• a transform iterator

Possibly also (if not too difficult to implement)

• a chain iterator
• a dropwhile

[Ichthyostega]

did the first steps here, due to the ContentsQuery, which can be implemented quite elegantly with a filter on top of the scope enumeration capability of the PlacementIndex

[Ichthyostega]

implemented an transform iterator, allowing to define PlacementIndex::iterator in terms of an transformer and a range yielded from the embedded hashtable

[Ichthyostega]

added caching to FilterIter, implemented duplicate-filtering iterator

[Ichthyostega]

(In #486) ugly, but not an urgent problem right now. Pushing to future

[Ichthyostega]

The basics are implemented and have proven to be very helpful already. Leaving the extensions to be done on demand.

[Undercover Agent]

Migration MasterTickets ⟼ Subtickets-plugin

[Ichthyostega]

Last days I made a complete overhaul, basically a rewrite of this frequently-used library header. The rationale is to minimise the overlap with IterExplorer — the »Itertools« are now considered the simple lightweight variant and preferred in cases where using the full-fledged pipeline builder framework seems like overkill. Another motivation was the fact that the »sandwich design« employed in the old implementation looked clumsy and dated; especially the fact that a specialised tool class must be instantiated and then moved into the base wrapper was found to be problematic and occasionally caused some correctness problems, especially when lambdas with reference-closure were bound.

The new design is oriented towards being inlineable, by avoiding the opaque std::function adapter and rather incorporating the nested functor directly.