Add splitByIndex

[ajaychandran]

Airstream provides a split operator that can used to improve the rendering performance of a list of elements. However this only works if the element can be mapped to a unique key (or in other words, the list has no duplicates).

A list with duplicates could be handled by using the index of an element as a key. WDYT?

[raquo]

Hm... seems like splitByIndex can be DIY-d with something like observable.map(_.zipWithIndex).split(_._2)(...)?

What are you rendering that you care to reuse elements by index – logs or something? There's also children.command in Laminar for special cases. Its use case is quite limited, but really works well when that's what you need.

[ajaychandran]

I have Signal containing a list of non-unique elements that each map to an image. Using observable.map(_.zipWithIndex).split(_._2)(...) works but requires creating an intermediate list.

[raquo]

I'd like to hear if anyone else wants this. Adapting the current implementation of split would complicate the code used for all existing usages of split. Alternatively, writing a separate implementation that's mostly redundant would not be very elegant (double that since a separate impl is required for streams and signals). So... I'll wait for more demand for this.