Are there any functional languages that don't have garbage collection

Question

Or even heavily functional styles in non functional/non memory managed languages. What sort of techniques are there to deal with problems like intermediate garbage? Cleaning up after lazynizess/thunk allocated memory. Performance(since you can't easily share resources between immutable variables if you have to track its progress to deallocate it(smart pointers?)

Answer 1

You might be interested in programming languages with linear or uniqueness types, these can manage resources (and memory in particular). Recent examples: ATS and LinearML.

There have been attempts at "region-based memory management" (e.g. Cyclone), but they haven't lifted off just yet -- regions also allow for (earlier) memory reclamation, but they aren't enough (e.g., there are programs which, when run with region-based memory management, will exhibit unacceptable performance). The two schemes could be mixed, I think.

Back to your question, some ATS programs can run without garbage collection. (I won't say that such programs are written in "functional" style, such as in SML, but in a mix of imperative and first-order functional style.)

Answer 2

The only relevant thing I can think of is how Mlton is eliminating a significant part of garbage collection with a region analysis. It should be possible, in theory, to implement a compiler which will treat an unmanageable and un-annotated pointer leak as an error, and then one would be able to use many functional programming techniques in an entirely manual memory management setting.