[repetae]

NuPRL hasn't been actively developed in 30 years and was only ever of interest to small group of people working on proof assistants and pure type theory, not industrial users. LiquidHaskell is actively developed and can be used in production today for real life industrial use cases.

[jonsterling]

Nuprl is absolutely still actively developed, in fact; I am constantly in touch with the PRL group. But the code-base is very crufty. In the past two years, though, numerous features have been added (including nominal abstraction, exceptions, bar induction, and a number of other interesting things), which you'd be aware of if you spent more time paying attention and less time snarking.

I am not at all telling people, "Switch from Liquid Haskell to Nuprl!". I'm providing perspective on the design space.