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| Description |
There are two principal string types used internally by GHC:
FastString:
* A compact, hash-consed, representation of character strings.
* Comparison is O(1), and you can get a Unique.Unique from them.
* Generated by fsLit.
* Turn into Outputable.SDoc with Outputable.ftext.
LitString:
* Just a wrapper for the Addr# of a C string (Ptr CChar).
* Practically no operations.
* Outputing them is fast.
* Generated by sLit.
* Turn into Outputable.SDoc with Outputable.ptext
Use LitString unless you want the facilities of FastString.
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| Synopsis |
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| FastStrings
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| data FastString |
A FastString is an array of bytes, hashed to support fast O(1)
comparison. It is also associated with a character encoding, so that
we know how to convert a FastString to the local encoding, or to the
Z-encoding used by the compiler internally.
FastStrings support a memoized conversion to the Z-encoding via zEncodeFS.
| | Constructors | |  Instances | |
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| Construction
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| fsLit :: String -> FastString |
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| mkFastString :: String -> FastString |
| Creates a UTF-8 encoded FastString from a String
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| mkFastStringBytes :: Ptr Word8 -> Int -> FastString |
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| mkFastStringByteList :: [Word8] -> FastString |
| Creates a FastString from a UTF-8 encoded [Word8]
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| mkFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString |
| Create a FastString from an existing ForeignPtr; the difference
between this and mkFastStringBytes is that we don't have to copy
the bytes if the string is new to the table.
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| mkFastString# :: Addr# -> FastString |
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| mkZFastString :: String -> FastString |
| Creates a Z-encoded FastString from a String
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| mkZFastStringBytes :: Ptr Word8 -> Int -> FastString |
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| Deconstruction
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| unpackFS :: FastString -> String |
| Unpacks and decodes the FastString
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| bytesFS :: FastString -> [Word8] |
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| Encoding
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| isZEncoded :: FastString -> Bool |
| Returns True if the FastString is Z-encoded
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| zEncodeFS :: FastString -> FastString |
| Returns a Z-encoded version of a FastString. This might be the
original, if it was already Z-encoded. The first time this
function is applied to a particular FastString, the results are
memoized.
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| Operations
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| uniqueOfFS :: FastString -> FastInt |
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| lengthFS :: FastString -> Int |
| Returns the length of the FastString in characters
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| nullFS :: FastString -> Bool |
| Returns True if the FastString is empty
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| appendFS :: FastString -> FastString -> FastString |
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| headFS :: FastString -> Char |
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| tailFS :: FastString -> FastString |
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| concatFS :: [FastString] -> FastString |
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| consFS :: Char -> FastString -> FastString |
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| nilFS :: FastString |
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| Outputing
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| hPutFS :: Handle -> FastString -> IO () |
| Outputs a FastString with no decoding at all, that is, you
get the actual bytes in the FastString written to the Handle.
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| Internal
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| getFastStringTable :: IO [[FastString]] |
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| hasZEncoding :: FastString -> Bool |
| Returns True if this FastString is not Z-encoded but already has
a Z-encoding cached (used in producing stats).
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| LitStrings
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| type LitString = Ptr Word8 |
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| Construction
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| sLit :: String -> LitString |
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| mkLitString# :: Addr# -> LitString |
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| mkLitString :: String -> LitString |
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| Deconstruction
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| unpackLitString :: LitString -> String |
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| Operations
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| lengthLS :: LitString -> Int |
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| Produced by Haddock version 2.3.0 |
