Lexer.x: Change the parser monad type P to allow the remaining input to
be returned after a partial parse. Add function
runPartial :: P t -> String -> Either (Posn, String) (String, t)
Parser.y: Add a partial parser pTerm for nonterminal Exp1.
Re-export runPartial.
1. The default encoding is changed from Latin-1 to UTF-8.
2. Alternate encodings should be specified as "--# -coding=enc", the old
"flags coding=enc" declarations have no effect but are still checked for
consistency.
3. A transitional warning is generated for files that contain non-ASCII
characters without specifying a character encoding:
"Warning: default encoding has changed from Latin-1 to UTF-8"
4. Conversion to Unicode is now done *before* lexing. This makes it possible
to allow arbitrary Unicode characters in identifiers. But identifiers are
still stored as ByteStrings, so they are limited to Latin-1 characters
for now.
5. Lexer.hs is no longer part of the repository. We now generate the lexer
from Lexer.x with alex>=3. Some workarounds for bugs in alex-3.0 were
needed. These bugs might already be fixed in newer versions of alex, but
we should be compatible with what is shipped in the Haskell Platform.
The fact that identifiers are represented as ByteStrings is now an internal
implentation detail in module GF.Infra.Ident. Conversion between ByteString
and identifiers is only needed in the lexer and the Binary instances.
Most of the explicit uses of ByteStrings were eliminated by using identS,
identS = identC . BS.pack
which was found in GF.Grammar.CF and moved to GF.Infra.Ident. The function
prefixIdent :: String -> Ident -> Ident
allowed one additional import of ByteString to be eliminated. The functions
isArgIdent :: Ident -> Bool
getArgIndex :: Ident -> Maybe Int
were needed to eliminate explicit pattern matching on Ident from two modules.
The parser works on raw byte sequences read from source files. If parsing
succeeds the raw byte sequences are converted to proper Unicode characters
in a later phase. But the parser calls the function buildAnyTree, which can
fail and generate error messages containing source code fragments, which might
then containing raw byte sequences. To render these error messages correctly,
they need to be converted in accordance with the coding flag in the source
file. This is now done for UTF-8-encoded source files, but should ideally also
be done for other character encodings. (Latin-1-encoded files never suffered
from this problem, since raw bytes are proper Unicode characters in this case.)
