The phantom polymorphic variant qualifying AST nodes is reversed:
- previously, we were explicitely restricting each AST node to the passes where it belonged using a closed type (e.g. `[< dcalc | lcalc]`)
- now, each node instead declares the "feature" it provides using an open type (e.g. `[> 'Exceptions ]`)
- then the AST for a specific pass limits the features it allows with a closed type
The result is that you can mix and match all features if you wish,
even if the result is not a valid AST for any given pass. More
interestingly, it's now easier to write a function that works on
different ASTs at once (it's the inferred default if you don't write a
type restriction).
The opportunity was also taken to simplify the encoding of the
operators, which don't need a second type parameter anymore.
This is a hack, but not a dirty one: a new command `catala pygmentize` is added,
which is just a wrapper around `pygmentize` that calls it with the proper lexers
defined.
The point is that this needs no installation, just a stock `pygmentize`
installation and the `catala` binary.
This leverages the embedded lexer already used for HTML output, and uses the
LaTeX pygments backend to colorise code directly, without the need for `minted`.
Changelog:
---
A lot has been going on, with more than 530 patches and 70 PRs merged since
0.7.0 last summer. In summary:
- Quite a lot of syntax improvements and changes. Checkout the latest
[cheat-sheet](https://catalalang.github.io/catala/syntax.pdf) for an overview
- Allow local `let ... equals ... in ...` definitions
- Better error messages and positions throughout
- Added the ability to directly call a scope and retrieve its outputs, like a
function
- Added disambiguation, allowing to access structure fields without specifying
the structure type each time
- Added automated resolution of operators, allowing e.g. to write just `+` in
place of all the type-specific operators `+.`, `+$`, `+@`, `+^`, etc.
- More consistent priority for operators. It is no longer allowed to write `a
and b or c` without parenthesis.
- Added and changed some operators (`date + duration` now allowed either way,
`int / int` now returns a decimal, added `duration / duration`)
- Added the ability to have variables and functions defined at
top-level (outside of any scope). See annex A of the tutorial for details.
- Added support for functions with multiple arguments
- Some big refactors in the compiler, allowing much better code sharing between
the different passes, and making it much easier to extend. Also added the
possibility to run the type-checker earlier, etc.
- Countless bug-fixes
- Improvements to our proof backend with Z3
- A tool to automatically synchronise with the upstream French law from
Legifrance
Previously the `state` marker for rules was in a weird position:
```catala
rule foo under condition bar
consequence state st fulfilled
```
This patch unifies the syntax with definitions, now using instead:
```catala
rule foo state st
under condition bar
consequence fulfilled.
```
Interstingly enough, it was already implemented in the Python backend.
Required to implement *pro rata temporis*, which the US tax section 121 does
make use of.
Only allowed for durations expressed in days (as returned by `<date> - <date>`),
of course.
This adds a few positions to the parser, and tweaks some others, vastly
improving the reporting of some errors (inconsistent functions definitions, but
also exceptions cycles, etc.)
Changed the typing printing in the pretty printer to:
* () -> unit for empty lists
* a -> b for single elements lists
* (a, b, c, d) -> b for multiple elements lists
Since functions inside catala can now have multiple arguments (while
not yet being user-definable) the invariant is now about partial
evaluation not being possible.
