https://github.com/thblt/hsbang

Run Haskell programs as if they were scripts, without the interpreter overhead
https://github.com/thblt/hsbang

Last synced: 8 months ago
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Run Haskell programs as if they were scripts, without the interpreter overhead

• Host: GitHub
• URL: https://github.com/thblt/hsbang
• Owner: thblt
• License: gpl-3.0
• Created: 2018-05-03T15:34:49.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2018-05-03T17:20:36.000Z (about 8 years ago)
• Last Synced: 2025-02-16T01:25:26.891Z (over 1 year ago)
• Language: Shell
• Size: 15.6 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.org
  • License: LICENSE

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README

          
#+TITLE: hsbang

Scripting in Haskell is difficult because of two issues: compatibility

and performance.  [[https://docs.haskellstack.org/en/stable/README/][Stack]] solves the compatibility issue by behaving as

a [[https://docs.haskellstack.org/en/stable/GUIDE/#script-interpreter][script interpreter]], but performance so far is horrible: on my

machine, a /Hello, world!/ takes more than 1s to run.

=hsbang= is a shebang pseudo-interpreter for Haskell programs using

Stack, but instead of actually running the script on an interpreter,

it calls =stack= and =ghc= to compile it to native code, and caches the

resulting binary.  If the same script is called again, the cached

binary is run.  Performance is incomparable:

#+BEGIN_EXAMPLE

$ ./hello.stack

Hello, world!

/hello.stack  1,04s user 0,17s system 101% cpu 1,191 total

$ ./hello.hsbang

Hello, world!

/hello.hsbang  0,01s user 0,01s system 100% cpu 0,027 total

#+END_EXAMPLE

Yes, that's 44 times faster.

* Usage

=hsbang= is a shebang interpreter.  To use it to write an Haskell script, all you have to do is:

#+BEGIN_SRC haskell

  #!/usr/bin/env hsbang

  -- stack --resolver=lts-11.7 --package ncurses

  import UI.NCurses

  main :: IO ()

  main = runCurses $ do

      setEcho False

      w <- defaultWindow

      updateWindow w $ do

          moveCursor 1 10

          drawString "Hello world!"

          moveCursor 3 10

          drawString "(press q to quit)"

          moveCursor 0 0

      render

      waitFor w (\ev -> ev == EventCharacter 'q' || ev == EventCharacter 'Q')

  waitFor :: Window -> (Event -> Bool) -> Curses ()

  waitFor w p = loop where

      loop = do

          ev <- getEvent w Nothing

          case ev of

              Nothing -> loop

              Just ev' -> if p ev' then return () else loop

#+END_SRC