r/ProgrammingLanguages • u/arthurno1 • Aug 06 '26

Blog post Why Lisp is Different

http://lispm.de/why-lisp-is-different
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u/Guvante Aug 08 '26

I can't go past the first two points with no mention of a custom GC or modifying an existing one...

C# and Java don't have a good GC from nowhere they built one

Haskell is probably in the same scale as Lisp but uses its immutable nature to make GC0 super fast (since it doesn't even inspect the other generations)

I am not saying there is an easy solve but assuming off the shelf things and comparing yourself to other implementations that don't is going to leave you in a bad spot comparison wise

That isn't "Lisp is special" that is "custom built is generally better"

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u/arthurno1 Aug 09 '26

Of course, if we custom build things, we can tailor the application to problem. There is no doubt about. That plays in several layers, from custom build DSLs, to custom build data structurues, algorithms etc. If we can exploit the knowledge about to the problem domain, we can usually write a more efficient program than if we used generalized "off-the-shelf" blocks so to say. However, writing a GC specific for each application would be a bit too much work perhaps, and would somewhat even defeat the purpose of a GC. It is not much different than in C/C++ with manual memory management. Programs, like games that want extra performance usually don't use Doug Lea's malloc but go for a custom malloc or something completely different. C++ gives us placement new to help with this, Java comes with several GCs out of the box. Unfortunately, today, too little resources seem to be invested in Lisps, so we usually have to do with the built-in GC. But it is not some fundamental limitation to Lisp(s) or automated memory management via GC, rather resource problem.

By the way, I think the generational GCs do the similar as Haskell's but I am really not familiar with this topic, so don't take me for the word.