QuasiQuoter for interpolated strings using Perl 6 syntax.

The q form does one thing and does it well: It contains a multi-line string with no interpolation at all:

 {-# LANGUAGE QuasiQuotes, ExtendedDefaultRules #-} import Text.InterpolatedString.Perl6 (q) foo :: String foo = [$q| Well here is a multi-line string! |] 

The qc form interpolates curly braces: Expressions inside {} will be directly interpolated if it's a String, or have show called if it is not.

Escaping of '{' is done with backslash.

For interpolating numeric expressions without an explicit type signature, use the ExtendedDefaultRules lanuage pragma, as shown below:

 {-# LANGUAGE QuasiQuotes, ExtendedDefaultRules #-} import Text.InterpolatedString.Perl6 (qc) bar :: String bar = [$qc| Well {"hello" ++ " there"} {6 * 7} |] 

bar will have the value " Well hello there 42 ".

If you want control over how show works on your types, define a custom ShowQ instance:

 import Text.InterpolatedString.Perl6 (qc, ShowQ(..)) instance ShowQ ByteString where showQ = unpack 

That way you interpolate bytestrings will not result in double quotes or character escapes.

The qq form adds to the qc form with a simple shorthand: '$foo' means '{foo}', namely interpolating a single variable into the string.

 {-# LANGUAGE QuasiQuotes, ExtendedDefaultRules #-} import Text.InterpolatedString.Perl6 (qq) baz :: String baz = [$qc| Hello, $who |] where who = World 

The ability to define custom ShowQ instances is particularly powerful with cascading instances using qq.

Below is a sample snippet from a script that converts Shape objects into AppleScript suitable for drawing in OmniGraffle:

 {-# LANGUAGE QuasiQuotes, ExtendedDefaultRules, NamedFieldPuns, RecordWildCards #-} import qualified System.IO.UTF8 as UTF8 import Text.InterpolatedString.Perl6 

 data Shape = Shape { originX :: Int , originY :: Int , width :: Int , height :: Int , stroke :: Stroke , text :: Text } instance ShowQ Shape where showQ Shape{..} = [$qq| make new shape at end of graphics with properties \{ $text, $stroke, _size, $_origin } |] where _size = [$qq|size: {$width, $height}|] _origin = [$qq|origin: {$originX, $originY}|] 

 data Stroke = StrokeWhite | StrokeNone instance ShowQ Stroke where showQ StrokeNone = "draws stroke:false" showQ StrokeWhite = "stroke color: {1, 1, 1}" 

 data Text = Text { txt :: String , color :: Color } instance ShowQ Text where showQ Text{..} = [$qq|text: \{ text: "$txt", $color, alignment: center } |] 

 data Color = Color { red :: Float, green :: Float, blue :: Float } instance ShowQ Color where showQ Color{..} = [$qq|color: {$red, $green, $blue}|] 

 main :: IO () main = UTF8.putStrLn [$qq| tell application "OmniGraffle Professional 5" tell canvas of front window { makeShape ... } end tell end tell |]