[Haskell-cafe] ANNOUNCE: hoppy, qtah

Bryan Gardiner bog at khumba.net
Mon Feb 8 18:11:36 UTC 2016

Are you sick and tired of the ease with which Haskell code flows onto
the page?  Even the thrill of binding to a C library losing its
lustre?  Look no further!  I present to you a tool restoring the good
old days of pointer arithmetic, manual memory management, and hours
lost to the debugger:

Hoppy is a new C++ FFI generator for Haskell.  It takes Haskell code
that describes a C++ API, and generates C++ and Haskell code to allow
the two languages to interact.  It supports a good subset of C++,
including functions, classes, variables, enums and bitflags, operator
overloading, constness, and simple templates.  Adding a function takes
only a few lines of code, and you normally don't need to write C++
yourself.  For example, a definition for std::string is:

    c_string :: Class
    c_string =
      addReqIncludes [includeStd "string"] $
      classAddFeatures [Assignable, Comparable, Copyable, Equatable] $
      makeClass (ident1 "std" "string") (Just $ toExtName "StdString") []
      [ mkCtor "new" []
      , mkCtor "newFromCString" [TPtr $ TConst TChar]
      [ mkConstMethod' "at" "at" [TInt] $ TRef TChar
      , mkConstMethod' "at" "get" [TInt] TChar
      , mkConstMethod "c_str" [] $ TPtr $ TConst TChar
      , mkConstMethod "size" [] TSize
      , mkConstMethod OpAdd [TObj c_string] $ TObj c_string

Now, writing a FFI generator isn't much fun unless you have a project
to use it with.  So I am pleased to also announce Qtah, a fresh set of
Qt 4/5 bindings.  These include portions of QtCore, QtGui, and
QtWidgets, and are on the whole wildly incomplete, but are usable for
basic tasks so far, and I am working on extending coverage.

(On qtHaskell/hsQt: I started Qtah before qtHaskell began being
updated in 2015 and I missed when that happened.  My hope is that Qtah
requires less code and effort to maintain; at least, qtHaskell
contains a lot of generated code and I haven't seen where it came
from, so please correct me if the generator is in fact available
somewhere.  Hoppy also doesn't (currently) do many of the fancy things
that qtHaskell does, like overloading and garbage collection.)

Both Hoppy and Qtah are young, and I am very interested in discussing
how to make them most useful for the community.  Because of questions
such as this[1], their APIs (including those of generated bindings)
should be considered experimental at this time.

I will be uploading Hoppy to Hackage shortly.  Becuase Qtah includes a
shared library, I haven't figured out how to get that on Hackage yet,
so you'll have to clone the repo yourself.



Happy hacking!

Bryan Gardiner

[1] https://gitlab.com/khumba/hoppy/issues/3
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