audreyt / Interpolatedstring Perl6

Text.InterpolatedString.Perl6

QuasiQuoter for Perl6-style multi-line interpolated strings with "q", "qq" and "qc" support.

Description

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 -- Text, ByteString etc also works foo = [q|

Well here is a multi-line string!

|]

Any instance of the IsString class is permitted.

The qc form interpolates curly braces: expressions inside {} will be directly interpolated if it's a Char, String, Text or ByteString, or it will 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:

For example, this instance allows you to display interpolated lists of strings as a sequence of words, removing those pesky brackets, quotes, and escape sequences.

{-# LANGUAGE FlexibleInstances #-} import Text.InterpolatedString.Perl6 (qc, ShowQ(..)) instance ShowQ [String] where showQ = unwords

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"

Both qc and qq permit output to any types with both IsString and Monoid instances.

{-# LANGUAGE QuasiQuotes, OverloadedStrings #-} import Text.InterpolatedString.Perl6 (qc) import Data.Text (Text) import Data.ByteString.Char8 (ByteString) qux :: ByteString qux = [qc| This will convert {"Text" :: Text} to {"ByteString" :: ByteString} |]

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 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 = putStrLn [qq| tell application "OmniGraffle Professional 5" tell canvas of front window { makeShape ... } end tell end tell |]