granule VS frank

I believe both Gerty and Granule are implemented in Haskell and are the only implementations of GRTT.

Granule and the related Gerty languages feature graded modal types which afaiu can be used similar to linear types to specify the number of times a resource should be consumed in a function, which, unlike linear types, may be a variable amount instead of only exactly once.

How does this compare to other effect-oriented languages like Koka, Frank, and Eff?

I've been doing some work with Koka lately, but I briefly looked into the other three (including Effekt) and it mostly came down to, 'Koka seems most active in development'[1] and 'Koka had the easiest to use documentation for me'[2].

[1] E.g. https://github.com/effekt-lang/effekt had its last commit back in June; https://github.com/frank-lang/frank last commit last year; but https://github.com/koka-lang/koka last update was Oct 15. Effekt seems semi-active, at least, compared to Frank. While stability is good, I wouldn't expect it in a language actively being used for research.

[2] Comparing https://koka-lang.github.io/koka/doc/book.html and https://effekt-lang.org/docs/ and https://www.eff-lang.org/learn/

Frank's effect handling. "A strict functional programming language with a bidirectional effect type system designed from the ground up around a novel variant of Plotkin and Pretnar's effect handler abstraction. ... Frank [is different from other PLs with effect type systems in that it is based on] generalising the basic mechanism of functional abstraction itself. A function is simply the special case of a Frank operator that interprets no commands. Moreover, Frank's operators can be multihandlers which simultaneously interpret commands from several sources at once, without disturbing the direct style of functional programming with values. Effect typing in Frank employs a novel form of effect polymorphism which avoid mentioning effect variables in source code. This is achieved by propagating an ambient ability inwards, rather than accumulating unions of potential effects outwards."