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README
hs-duktape
Haskell bindings for duktape, a very compact embedded ECMAScript (JavaScript) engine.
Usage
Here's a simple REPL example:
module Main where
import Scripting.Duktape
import Control.Monad (forever)
import Data.ByteString.Char8 (pack)
import System.IO (hFlush, stdout)
main :: IO ()
main = do
dukm <- createDuktapeCtx
case dukm of
Nothing -> putStrLn "I can't even (start Duktape)"
Just duk -> forever $ do
putStr "duktape> "
hFlush stdout
retVal <- evalDuktape duk =<< return . pack =<< getLine
case retVal of
Left e -> putStrLn $ "Duktape error: " ++ e
Right Nothing -> putStrLn "No result"
Right (Just v) -> print v
Aeson's Value type is used for exchanging values between Haskell and ECMAScript.
lens-aeson is a good library for working with Value, um, values.
You can also call functions that are on the global object (or any object that's on the global object):
dukm <- createDuktapeCtx
bresult <- callDuktape (fromJust dukm) Nothing "boolTest" [Bool True, Bool True, Bool False] -- boolTest(true, true, false)
aresult <- callDuktape (fromJust dukm) (Just "NumFuns") "sum" [Number 1, Number 2] -- NumFuns.sum(1, 2)
And expose Haskell functions (same as with calls: set on global or a property of global):
dukm <- createDuktapeCtx
let dbl (Number x) = return $ Number $ x * 2 :: IO Value
dbl _ = return $ String "wtf"
reD <- exposeFnDuktape (fromJust ctx) Nothing "double" dbl
The functions must be of type IO (), IO Value, Value -> IO Value, Value -> Value -> IO Value... and so on.
(Or with any ToJSON/FromJSON values instead of Value)
Advanced: Script execution timeout
Instead of createDuktapeCtx, you can use createGovernedHeap to enforce termination via a timeout:
allowQuarterSecond :: IO (IO Bool)
allowQuarterSecond = do
initializedAt <- getCurrentTime
return $ do
now <- getCurrentTime
let diff = diffUTCTime now initializedAt
return $ diff > 0.25
guvnor <- allowQuarterSecond
ctx <- createGovernedHeap nullFunPtr nullFunPtr nullFunPtr guvnor nullFunPtr
result <- evalDuktape (fromJust ctx) "while (true) {}"
-- Left "RangeError: execution timeout"
Development
Note: The duktape configure script invoked by Cabal/Stack requires python 2 with the PyYAML library installed. pip install PyYAML is one way to achieve this.
Use stack to build.
$ stack build
$ stack test && rm tests.tix
Contributing
Please feel free to submit pull requests!
By participating in this project you agree to follow the Contributor Code of Conduct.
The list of contributors is available on GitHub.
License
Licensed under the MIT license (see to the LICENSE file).
Haskell bindings: Copyright (c) 2015-2018 Greg V [email protected]
Duktape: Copyright (c) 2013-2016 by Duktape authors (see duktape/AUTHORS.rst)
*Note that all licence references and agreements mentioned in the hs-duktape README section above
are relevant to that project's source code only.