Merge branch 'release-4.2' into src. Close #58.

home.md

@@ -1,33 +1,68 @@
 ## News
-**Release 3.20 -- 2024-07-07**
+**Release 4.2 -- 2025-01-07**
 
-We are pleased to announce the release of Copilot 3.20, a stream-based DSL
-for writing and monitoring embedded C programs, with an emphasis on correctness
-and hard realtime requirements. Copilot is typically used as a high-level
-runtime verification framework, and supports temporal logic (LTL, PTLTL and
-MTL), clocks and voting algorithms.
+We are pleased to announce the release of Copilot 4.2, a stream-based DSL for
+writing and monitoring embedded C programs, with an emphasis on correctness and
+hard realtime requirements. Copilot is typically used as a high-level runtime
+verification framework, and supports temporal logic (LTL, PTLTL and MTL),
+clocks and voting algorithms.
 
 Among others, Copilot is being used at the Safety Critical Avionics Systems
 Branch of NASA Langley Research Center for monitoring test flights of drones.
 
-This release introduces support to upload the values of fields in structs, and
-add support for GHC 9.8. We also remove deprecated functions from
-`copilot-language` that had been renamed in prior versions for compatibility
-with newer versions of GHC.
+This release introduces several big improvements to Copilot:
+
+- Specifications can now use the same handler for multiple monitors, provided
+  that the arguments to those handlers always have consistent types and arity.
+This simplifies the code that uses Copilot, since it's no longer necessary to
+create multiple boilerplate wrappers around the same handling routines.
+
+- The use of structs has been vastly simplified. Before, it was necessary to
+  define class instances for structs, whose implementations were, although
+repetitive, not intuitive especially for users unfamiliar with Haskell. In
+Copilot 4.2, it is now possible to define those methods automatically by
+relying on default method implementations that work well for most cases,
+although users retain the ability to customize those methods if desired.
+
+- We have increased test coverage in `copilot-core`, reaching full coverage of
+  the public interface.
+
+The interface of `copilot-core` has also been simplified, deprecating record
+fields of an existential type UExpr, which were largely unused outside of
+Copilot's internals.
+
+The new implementation is compatible with versions of GHC from 8.6 to 9.10, as
+well as with the Stackage Nightly.
+
+This release has been made possible thanks to key submissions from Frank Dedden
+(@fdedden), Ryan Scott (@RyanGlScott), and Kyle Beech (@kaBeech), the last of
+which is also a first-time contributor to the project. We are grateful to them
+for their timely contributions, especially during the holidays, and for making
+Copilot better every day. We also want to thank the attendees of Zurihac 2024
+for technical discussions that helped find the right solutions to some of the
+problems addressed by this release.
 
 Details are available
-[here](https://github.com/Copilot-Language/copilot/milestone/27?closed=1),
+[here](https://github.com/Copilot-Language/copilot/milestone/30?closed=1),
 and
-[here](https://github.com/Copilot-Language/copilot/releases/tag/v3.20).
+[here](https://github.com/Copilot-Language/copilot/releases/tag/v4.2).
+
+As always, we're releasing exactly 2 months since the last release. Our next
+release is scheduled for Mar 7th, 2025.
 
-Current emphasis is on introducing support to update the values of elements in
-arrays, improving the codebase in test coverage, removing unnecessary
-dependencies, hiding internal definitions, and formatting the code to meet our
-new coding standards. We also plan to add extensions to be able to visualize
-streams. Users are encouraged to participate by opening issues and asking
-questions via our [github repo](https://github.com/copilot-language/copilot).
+We want to remind the community that Copilot is now accepting code
+contributions from external participants again. Please see the discussions and
+the issues to learn how to participate.
+
+Current emphasis is on improving the codebase in terms of performance,
+stability and test coverage, removing unnecessary dependencies, hiding internal
+definitions, formatting the code to meet our new coding standards, and
+simplifying the Copilot interface. Users are encouraged to participate by
+opening issues, asking questions, extending the implementation, and sending bug
+fixes via our [github repo](https://github.com/copilot-language/copilot).
 
 ## License
+
 Copilot is distributed under the BSD-3-Clause license, which can be found
 [here](https://raw.githubusercontent.com/Copilot-Language/Copilot/master/LICENSE).