46 lines
1.9 KiB
TeX
46 lines
1.9 KiB
TeX
% Brittany-LB.tex
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\begin{hcarentry}[updated]{Brittany}
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\report{Lennart Spitzner}%11/17
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\status{work in progress}
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\makeheader
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Brittany is a Haskell source code formatting tool. It is based on
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ghc-exactprint and thus uses the ghc parser, in contrast to tools based on
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haskell-src-exts such as hindent or haskell-formatter.
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The goals of the project are to:
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\begin{compactitem}
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\item support the full ghc-haskell syntax including syntactic extensions;
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\item retain newlines and comments unmodified (to the degree possible when
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code around them gets reformatted);
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\item be clever about using horizontal space while not overflowing it if it
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cannot be avoided;
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\item have linear complexity in the size of the input text / the number of
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syntactic nodes in the input.
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\item support horizontal alignments (e.g. different equations/pattern matches
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in the some function's definition).
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\end{compactitem}
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In contrast to other formatters brittany internally works in two steps:
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Firstly transforming the syntax tree into a document tree representation,
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similar to the document representation in general-purpose pretty-printers such
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as the \emph{pretty} package, but much more specialized for the specific
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purpose of handling a Haskell source code document. Secondly this document
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representation is transformed into the output text document. This approach
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allows to handle many different syntactic constructs in a uniform way, making
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it possible to attain the above goals with a manageable amount of work.
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Brittany is work in progress; currently only type signatures and function
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bindings are transformed, and not all syntactic constructs are supported.
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Nonetheless Brittany is safe to try/use as there are checks in place to ensure
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that the output is syntactically valid.
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Brittany requires ghc-8.*, and is available on Hackage and on Stackage.
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\FurtherReading
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\begin{compactitem}
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\item \url{https://github.com/lspitzner/brittany}
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\end{compactitem}
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\end{hcarentry}
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