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Hacker News now runs on top of Common Lisp


Hacker News was written in the Arc lisp dialect, a dialect created by Paul Graham. Arc was implemented on top of Racket, but that has now changed. HN runs on top of SBCL since a few months.But why? For performance reasons. I recently noticed that Hacker News no longer uses paging for long threads. In the past, when a discussion grew large, we had to click “More” to load the next page of comments, and dang would occasionally post helpful tips to remind us about this feature.

In the past, when a discussion grew large, we had to click “More” to load the next page of comments, and dang would occasionally post helpful tips to remind us about this feature. This isn’t novel, but it makes reimplementation easier since you pack as much as possible in the later stages, and only arc0 needs to be written in the underlying system (Racket, JS, or CL). Much of the HN codebase consists of anti-abuse measures that would stop working if people knew about them.

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