# Curry Frontend

The Curry frontend parses source files (`.curry`), emits errors and
warnings, performs various checks and transformations and 
generates FlatCurry (`.fcy`, `.fint`) or AbstractCurry (`.acy`, `.uacy`),
amonst other formats.

The project originated from a modified version of the Münster-Curry-Compiler
(MCC) for use with [PAKCS](https://git.ps.informatik.uni-kiel.de/curry/pakcs),
but can also be used with a variety of other backends, most notably including
[KiCS2](https://git.ps.informatik.uni-kiel.de/curry/kics2).

## Requirements

* `cabal-install`
* A recent version of the `curry-base` package, installed locally

## Building

To build the project, run `cabal v1-build`.

## Running

To run the project, use `cabal v1-run`.

Alternatively, you can launch the built executable manually from `dist/build/curry-frontend`.

## Usage

For a detailed overview of the available options, you can use the following command:

`curry-frontend --help`

### Available Formats

```
--flat  : Generate a FlatCurry (.fcy) and FlatInterface (.fint) file
--xml   : Generate a FlatXML (_flat.xml) file
--acy   : Generate a (type-inferred) AbstractCurry (.acy) file
--uacy  : Generate an untyped AbstractCurry (.uacy) file
```

The generation of an untyped AbstractCurry program is performed without
type checking (i.e. programs with type checks will compile). All functions
will either have the type signature specified in the source or, if not
available, the dummy type `prelude.untyped`.

FlatCurry files will always be generated for the imported modules,
since the interfaces are required for static-semantic analysis and type
inference (only for typed AbstractCurry).

## Remarks

- To use the PAKCS libraries (especially for the `Prelude`), the environment
  variable `PAKCS_LIB` has to point to the correct paths, e.g. using
  
  `export PAKCS_LIB=[pakcs path]/pacs/lib:[pakcs path]/pacs/lib/meta:...`

  where `[pakcs path]` is the directory containing the PAKCS distribution.

- In contrast to PAKCS, the frontend allow use of anonymous variables
  (denoted by an underscore `_`) in type declarations, e.g.
  
  ```curry
  data T _ = c
  ```

## Known Issues

[See GitLab](https://git.ps.informatik.uni-kiel.de/curry/curry-frontend/-/issues)