Inline IIFE & algorithms taking lambdas

[tmr232]

When I use IIFE, I think it's sometimes useful to think about it as part of the flow of the function. Probably as an optional flag.

In addition to those, many languages have looping constructs using lambdas, and we completely ignore those.
I am not entirely sure what the right way to include them is (maybe inline in a cluster?), but they are definitely worth exploring.