Definition
Plain language
A nested stack of functions that gets walked every time you access an entry — slow for big stacks.
As stated in the literature
In functional implementations of key-value stores, the linked chain of closures produced by representing the store as a function from key to value; access latency grows linearly with chain depth.
Why it matters: It's a reminder that elegant functional designs can hide painful linear-time access costs that matter once data grows.
For example, in a functional key-value store, looking up the 1000th most recent key may walk through a thousand nested functions before returning a value.
Heard on the show
“The reason is that Chapar's reference, like a lot of verified-code references, represents its store as a function from key to value — which extracts to a closure chain that grows with every Put.”Episode 075 — Growing Code and Proof Together: Verified Systems in Ten Hours Instead of a Year