ghcup-hs/lib/GHCup/Utils/String/QQ.hs

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{-# LANGUAGE TemplateHaskell #-}
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{-|
Module : GHCup.Utils.String.QQ
Description : String quasi quoters
Copyright : (c) Audrey Tang <audreyt@audreyt.org> 2019, Julian Ospald <hasufell@posteo.de> 2020
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License : LGPL-3.0
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Maintainer : hasufell@hasufell.de
Stability : experimental
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Portability : portable
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QuasiQuoter for non-interpolated strings, texts and bytestrings.
The "s" quoter contains a multi-line string with no interpolation at all,
except that the leading newline is trimmed and carriage returns stripped.
@
{-\# LANGUAGE QuasiQuotes #-}
import Data.Text (Text)
import Data.String.QQ
foo :: Text -- "String", "ByteString" etc also works
foo = [s|
Well here is a
multi-line string!
|]
@
Any instance of the IsString type is permitted.
(For GHC versions 6, write "[$s||]" instead of "[s||]".)
-}
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module GHCup.Utils.String.QQ
( s
)
where
import Data.Char
import GHC.Exts ( IsString(..) )
import Language.Haskell.TH.Quote
-- | QuasiQuoter for a non-interpolating ASCII IsString literal.
-- The pattern portion is undefined.
s :: QuasiQuoter
s = QuasiQuoter
(\s' -> case and $ fmap isAscii s' of
True -> (\a -> [|fromString a|]) . trimLeadingNewline . removeCRs $ s'
False -> fail "Not ascii"
)
(error "Cannot use q as a pattern")
(error "Cannot use q as a type")
(error "Cannot use q as a dec")
where
removeCRs = filter (/= '\r')
trimLeadingNewline ('\n' : xs) = xs
trimLeadingNewline xs = xs