Ugh, my brain has fogged over, can someone remind me how to collapse a list of lists into a single list containing the contents of all the lists?

flatten ?

Never mind I think I’ve just remembered a way (foldl append '() '((2 5 8) (1 3 10)))

@soegaard2 Thanks, flatten does indeed work and is tidier than my solution.

Thanks @philip.mcgrath for taking the thoroughly commented alternate solution. Especially for explaining the idea behind the helper function. This is extremely helpful in growing my understanding of Racket / Scheme.