GHC 8.10.1 is slated to be released
soon,
and among the improvements that it offers is the
new StandaloneKindSignatures language extension. Standalone kind
signatures (or “SAKS” for short) are like type signatures, except that they
describe type-level declarations instead of term-level values. Here is one
example of a standalone kind signature that describes the kind of a type
synonym:
Tuples, aside from their weird syntax, are just like any other data type.
You can even partially apply a tuple type constructor by writing it in
“prefix” style. For instance, (Int, Bool) and (,) Int Bool are two ways
of writing the same type. This flexibility allows tuples to be manipulated
in all the ways we’re used to in Haskell.
singletons-2.6
has been uploaded to Hackage, coming on the heels of GHC 8.8.1’s release. There
are many interesting things to say about this particular version of
singletons, and I invite you to check out the
changelog if you
want a quick overview.
Higher-rank types are a very widely used feature in GHC.
The RankNTypes language extension, which enables the use of higher-rank
types, has been around since GHC 6.8.1 (released in November 2007), and
by one metric, RankNTypes is the 15th most popular language extension in
use today [1].
According to Anish Tondwalkar’s blog post ↩
Partial application is one of the most useful tools in a Haskell programmer’s toolbelt. Since functions are just data, they can be passed around without being supplied any arguments, just as one would with any other value. Due to the ubiquity of higher-order functions in Haskell, the ability to partially apply things is extremely useful.
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