Idris2/CHANGELOG.md

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Changes since Idris 2 v0.1.0
----------------------------
The implementation is now self-hosted. To initialise the build, either use
the [bootstrapping version of Idris2](https://github.com/edwinb/Idris2-boot)
or build from the generated Scheme, using `make bootstrap`.
Compiler updates:
* Data types with a single constructor, with a single unerased arguments,
are translated to just that argument, to save repeated packing and unpacking.
(c.f. `newtype` in Haskell)
+ A data type can opt out of this behaviour by specifying `noNewtype` in its
options list. `noNewtype` allows code generators to apply special handling
to the generated constructor/deconstructor, for a newtype-like data type,
that would otherwise be optimised away.
* 0-multiplicity constructor arguments are now properly erased, not just
given a placeholder null value.
Language changes:
* `total`, `covering` and `partial` flags on functions now have an effect.
* %transform directive, for declaring transformation rules on runtime
expressions. Transformation rules are automatically added for top level
implementations of interfaces.
* A %spec flag on functions which allows arguments to be marked for partial
evaluation, following the rules from "Scrapping Your Inefficient Engine"
(ICFP 2010, Brady & Hammond)
Library additions:
* Additional file management operations in `base`
* New module in `base` for time (`System.Clock`)
* New modules in `contrib` for JSON (`Language.JSON.*`); random numbers
(`System.Random`)
Other improvements:
* Various performance improvements in the typechecker:
+ Noting which metavariables are blocking unification constraints, so that
they only get retried if those metavariables make progress.
+ Evaluating `fromInteger` at compile time.
+ In the run-time, reuse the old heap after garbage collection if it
hasn't been resized, to avoid unnecessary system calls.
* Extend Idris2's literate mode to support reading Markdown and OrgMode files.
For more details see: https://idris2.readthedocs.io/en/latest/reference/literate.html
* Fields of records can be accessed (and updated) using the dot syntax,
such as `r.field1.field2` or `record { field1.field2 = 42 }`.
For details, see https://idris2.readthedocs.io/en/latest/reference/records.html
Changes since Idris 1
---------------------
Everything :). For full details, see:
https://idris2.readthedocs.io/en/latest/updates/updates.html