command-qq

>>> import System.Command.QQ
>>> putStr =<< unlines . reverse . lines <$> [sh|cowsay "Hello, I am command-qq!"|]
                ||     ||
                ||----w |
            (__)\       )\/\
         \  (oo)\_______
        \   ^__^
 -------------------------
< Hello, I am command-qq! >
 _________________________

Install

% cabal install command-qq

Features

Quasiquotation syntax for external interpreters

>>> [sh_| echo hello world! |]
hello world!

Custom quasiquoters

ghci = quoter $ callCommand "ghc" ["-ignore-dot-ghci", "-e"]

Then you can use ghci in ghci!

>>> [ghci| putStrLn "hello world!" |] :: IO ()
hello world!

For more examples, see System.Command.QQ.Predef

Haskell values embedding

Let's define Embed instance for a custom data type:

data Bang = Bang

instance Embed Bang where
  embed Bang = "!"

Then you can use variables of Bang type in quoted strings!

>>> [sh_| echo hello#{Bang} |]
hello!
>>> let bang = Bang in [sh_| echo hello#{bang} |]
hello!

Note, command-qq does not support full Haskell in embeddings, only variables/constructors names and literals

DSLs

See examples/CommandT.hs