At the risk of being downflamed for not knowing something obvious, I see it as the gap between what standard runtime libraries provide (e.g. nice generic list,

At the risk of being downflamed for not knowing something obvious, I see it as the gap between what standard runtime libraries provide (e.g. nice generic list, stack, and queue classes) and the algorithms devs implement on top of them. A part of me wants to see all of the grotesque implementations of "visit every relationship in this tree" that get invoked when I click the "add comment" button on this.