On 20/08/2020 18.36, Ignat Insarov wrote:
Hello…
This function first appeared _(to my knowledge)_ in [a Stack Overflow answer][1]. I found it useful several times, and eventually [I extended it to a family of 4 derived functions][2]: `converge`, `convergeBy`, `fixp` and `fixpBy`.
* `convergeBy` is like `takeWhile` but with a binary predicate. * `converge` cuts a list at a point where it starts to repeat itself. * `fixp` takes the last element.
FWIW, I've had occasion to have to implement both converge and convergeBy (albeit in Scala), albeit very rarely. My case was one of post-processing a linear list of 'instructions' to remove useless ones -- e.g. adjacement push-pop, etc. Easier to do just do it be repeated application than trying to figure out how to do it in a single pass. +½ from me, I guess :)