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Update README.md

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Lennart Spitzner 2016-08-12 15:51:43 +02:00 committed by GitHub
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@ -3,6 +3,8 @@ haskell source code formatter
![Output sample](https://github.com/lspitzner/brittany/raw/master/brittany-sample.gif)
(see another demonstration in [Showcase.md](Showcase.md))
This project's goals roughly are to:
- Be idempotent (this also directly ensures that only valid haskell is
@ -14,15 +16,16 @@ This project's goals roughly are to:
- Be clever about aligning things horizontally.
- Have linear complexity in the size of the input.
At this point, these goals are completed to different degrees. It is not
ensured that only syntactically valid haskell is produced (yet), and coverage
of the project's testsuite is rather limited. By using ghc-exactprint as the
parser, brittany supports full ghc syntax including extensions, but many of the
more obscure cases are not handled yet. More importantly, only type-signatures
and function/value bindings are processed; other module elements (data-decls,
classes, instances, imports/exports etc.) are not
At this point, these goals are completed to different degrees.
Currently, only type-signatures and function/value bindings are processed;
other module elements (data-decls, classes, instances, imports/exports etc.) are not
transformed in any way; this extends to e.g. bindings inside class instance
definitions - they won't be touched (yet).
By using ghc-exactprint as the parser, brittany supports full ghc syntax including
extensions, but many of the less common syntactic elements (even of 2010 haskell) are
not handled.
There are cases where comments are not re-inserted properly (leading to an error or
to affected comments being placed at a different location than in the input).
The current algorithm is rather clever about horizontal space while still being
linear in the size of the input (although the constant factor is not small).
@ -33,18 +36,34 @@ linear in the size of the input (although the constant factor is not small).
- `-XCPP` is not officially supported (yet).
- ~~Some commandline flags mentioned in the help don't work yet (and won't even
be parsed correctly.)~~ (fixed in 0.4.0.0)
- ~~Creates a `brittany.yaml` config file _in the current directory_. I am aware
that this behaviour is not optimal.~~ (fixed in 0.5.0.0; now creates user
config file in `~/.brittany`; still reads `brittany.conf` in current dir if
present.)
- Currently some unhandled syntactical constructs don't raise errors; in such
cases the output will contain ghc-exactprint'ed code and some debugging
comment. This could easily make the output invalid haskell.
- ~~Creates a `brittany.yaml` config file _in the current directory_.~~
(fixed in 0.5.0.0; now creates user config file in `~/.brittany`;
still reads `brittany.yaml` in current dir if present.)
- ~~Currently some unhandled syntactical constructs don't raise errors~~
(fixed in 0.6.0.0)
- There are cases where comments are not copied to the output (this will
be detected and the user will get an error); there are other cases where
comments are moved slightly; there are also cases where comments result in
wonky newline insertion (although this should be a purely aesthetic issue.)
# Building
(This does not cover _installation_. TODO)
~~~~
mkdir brittany-project
cd brittany-project/
git clone https://github.com/lspitzner/butcher.git
git clone https://github.com/lspitzner/data-tree-print.git
git clone https://github.com/lspitzner/ghc-exactprint.git
git clone https://github.com/lspitzner/brittany.git
cat > cabal.project <<EOF
packages: data-tree-print butcher ghc-exactprint brittany
EOF
# cabal new-configure -w $PATH_TO_GHC_8
cabal new-build brittany/
~~~~
# Usage
- Currently one mode of operation: Transform a single module. By default read