BiGUL-1.0.0: CHANGELOG.md

1.0.0 Changes
=============

Version 1.0.0 is the first official release, and is *not* compatible with
0.9.0 and earlier development versions.

The targeted GHC version is 7.10; 8.0 support is postponed due to its
non–backward compatible revisions to Template Haskell.

* Module restructuring

    The module structure is refined and simplified, with `Generics.BiGUL.AST`
    changed to `Generics.BiGUL`, pattern matching functions extracted to
    `Generics.BiGUL.PatternMatching`, and `Generics.BiGUL.Lib` created to
    serve as a prelude. More specific library modules are placed under
    `Generics.BiGUL.Lib.`:

    - `Generics.BiGUL.Lib.List` is the place for list-processing library
      programs. For now the only inhabitant is the “BiFluX alignment”.

    - `Generics.BiGUL.Lib.HuStudies` contains some small, concrete examples
      illustrating the use of every BiGUL construct.

* `Generics.BiGUL.Skip` and `Generics.BiGUL.Dep` changed

    - The view type of `Skip` is not restricted to `()` anymore, but when
      skipping, the view should be determined by the source as specified by
      the new functional argument to `Skip` — we can perform `Skip f` on a
      source `s` if and only if the view is `f s`. The old `Skip` can be
      defined in terms of the new one as `Skip (const ())`. There is a helper
      function `skip = Skip . const` defined in `Generics.BiGUL.Lib`.

    - `Dep` has been reverted to the original version, used to ignore the
      second component of the view when it depends on the first (but not
      the source).

* Major changes to `Generics.BiGUL.TH`

    - `deriveBiGULGeneric` now supports `newtype`.

    - The `update` syntax now takes the source pattern as its first argument
      and the view pattern as its second argument. (Previously the view
      pattern comes first.)

    - `rearrV` and `update` now check at compile time whether all view
      information is used (forbidding wildcard in view patterns and requiring
      all view variables are used); also `rearrS` and `rearrV` check whether
      their first argument is a one-argument lambda-expression.

    - The branch construction syntax has been slimmed down to just four
      functions: `normal`, `normalSV`, `adaptive`, and `adaptiveSV`.

    - Normal branch constructing functions now take an additional argument
      specifying on the source an “exit condition”, which should be satisfied
      by the updated source after the branch body is executed. All the exit
      conditions in a `Case` statement should (ideally) be disjoint.
      Overlapping exit conditions are still allowed for fast prototyping,
      though — the putback semantics of 'Case' will compute successfully as
      long as the ranges of the branches are disjoint (regardless of whether
      the exit conditions are specified precisely enough).

* Error-reporting mechanism overhauled

    - The types of `put` and `get` from `Generics.BiGUL.Interpreter` are
      changed to produce simply `Maybe` results. When execution fails
      (producing `Nothing`), invoke `putTrace` and `getTrace` to see the
      exact failure and the execution trace leading to the failure.

    - The execution traces include intermediate sources and views; the types
      used in a BiGUL program are thus required to be instances of `Show`.

* Show instances for BiGUL programs removed

    There are two reasons: Functions, which are everywhere in BiGUL programs,
    cannot be shown; and worse, printing of recursive BiGUL programs will not
    terminate.