While revisiting the quicksort chapter in Grokking Algorithms, the author wondered how to expose the recursive call‑stack depth without external profilers. In Go, an anonymous closure can capture a counter variable, letting the function report its deepest recursion level as it sorts. This technique turns a textbook illustration into a live debugging aid.

The first example uses a zero‑index pivot. A variable zeroPivotMaxDepth is declared before the closure and updated whenever the current depth exceeds it. Running the code on an already‑sorted slice of eight integers yields a max depth of 8, while a shuffled slice drops the depth to 6, demonstrating the metric in action.

Switching to a middle‑index pivot produces the classic best‑case divide‑and‑conquer behavior. The middlePivotMaxDepth counter reports only four levels for a sorted array and five for a random order, roughly half the depth of the zero‑pivot version. Developers can embed similar closures in other recursive algorithms to surface performance characteristics during development.