[Haskell'-private] pragmas and annotations (RE: the record system)

Ben Rudiak-Gould Benjamin.Rudiak-Gould at cl.cam.ac.uk
Tue Feb 28 16:07:37 EST 2006

Malcolm Wallace wrote:
>   * If the first three bytes of the file are "{-#", then keep reading in
>     ASCII/Latin-1/whatever until you discover an ENCODING decl (or not).
>   * If the first six bytes of the file are one of the two possible
>     UTF-16 representations of "{-#", then assume UTF-16 with that
>     byte-encoding until we find the ENCODING decl.  (A missing decl in
>     this case would be an error.)
>   * If the first twelve bytes of the file are a UCS-4 representation of
>     "{-#" then ... you get the picture.
>   * For UTF-16 and UCS-4 variations, you must also permit the file to
>     begin with an optional byte-order mark (two or four bytes).

You'd also want to look for the UTF-8 BOM, which is very common in Windows.

As for literate source, I suppose you could forbid .lhs files from using 
UTF-16 or UCS-32 unless there's a BOM. Then unlit wouldn't need to know the 
encoding (I think), and the .hs heuristics would work on the output.

-- Ben

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