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kill Emacs swap file

This commit is contained in:
Patrick Thomson 2018-06-26 11:00:41 -04:00
parent fd44b23449
commit a1e5121e5b

View File

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module Numeric.Exts
( parseInteger
, hex
, oct
, bin
, attempt
, lengths
) where
import Control.Applicative
import Control.Monad hiding (fail)
import Data.Attoparsec.Text
import Data.Char (isDigit, isOctDigit)
import Data.Text
import Numeric
import Prelude hiding (fail, filter)
import Prologue
import Text.Read (readMaybe)
-- The ending stanza. Note the explicit endOfInput call to ensure we haven't left any dangling input.
lengths :: Parser ()
lengths = skipWhile (inClass "iIjJlL") *> endOfInput
-- Parse a hex value, leaning on the parser provided by Attoparsec.
hex :: Num a => Parser a
hex = do
void (char '0')
void (char 'x' <|> char 'X')
fromIntegral <$> hexadecimal @Integer <* lengths
-- We lean on Haskell's octal integer support, parsing
-- the given string as an integer then coercing it to a Scientific.
oct :: Num a => Parser a
oct = do
void (char '0')
optional (char 'o' <|> char 'O')
skipWhile (inClass "Oo") -- this can fail!
digs <- takeWhile1 isOctDigit <* lengths
fromIntegral <$> attempt @Integer (unpack ("0o" <> digs)) <* lengths
-- The case for binary literals is somewhat baroque. Despite having binary literal support, Integer's
-- Read instance does not handle binary literals. So we have to shell out to Numeric.readInt, which
-- is a very strange API, but works for our use case. The use of 'error' looks partial, but if Attoparsec
-- and readInt do their jobs, it should never happen.
bin :: (Show a, Num a) => Parser a
bin = do
void (char '0')
skipWhile1 (inClass "bB")
let isBin = inClass "01"
digs <- unpack <$> (takeWhile1 isBin <* lengths)
let c2b c = case c of
'0' -> 0
'1' -> 1
x -> error ("Invariant violated: both Attoparsec and readInt let a bad digit through: " <> [x])
let res = readInt 2 isBin c2b digs
case res of
[] -> fail ("No parse of binary literal: " <> digs)
[(x, "")] -> x <$ lengths
others -> fail ("Too many parses of binary literal: " <> show others)
-- Wrapper around readMaybe.
attempt :: Read a => String -> Parser a
attempt str = maybeM (fail ("No parse: " <> str)) (readMaybe str)
parseInteger :: Text -> Either String Integer
parseInteger = parseOnly integerParser
-- | A simplified version of parseScientific.
integerParser :: Parser Integer
integerParser = signed (choice [hex, oct, bin, dec]) where
dec = do
let notUnder = filter (/= '_')
let decOrUnder c = isDigit c || (c == '_')
contents <- notUnder <$> takeWhile1 decOrUnder
void lengths
attempt (unpack contents)