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hLibsass is a low-level binding to LibSass. It provides basic types used by the library along with a FFI interface to the C API.

This is really a low-level library, if you want a high-level, more Haskell-friendly library, check out hSass.

It is available on Hackage.

hLibsass' Changelog


This library is (mostly) 1-1 binding to LibSass. See LibSass wiki for documentation.

Static, shared or external version of LibSass?

hLibsass supports three different ways of linking with Libsass:

  1. Static, locally-built LibSass,
  2. Shared, locally-built LibSass, requires setting sharedLibsass flag,
  3. External (e.g. system package), requires setting externalLibsass flag.

The first two options rely on the LibSass being distributed with the hlibsass package and compiled during configure/build process. hLibsass is always distributed with LibSass version that is compatibile with the package.

Up until version, the first option was preferred, because LibSass has been distributed as a source package only. Development package of LibSass is now available in most Linux distributions and in Homebrew, so using it is equally good option

Using locally-built shared version of LibSass may require adjusting LD_LIBRARY_PATH or putting somewhere in the PATH, so this option is discouraged. However, if you really want to use it that way, you may use tools/ to set LD_LIBRARY_PATH (it extracts the library location using ghc-pkg).

externalLibsass flag has precedence over sharedLibsass.

hLibsass and LibSass version

hLibsass uses LibSass internally and therefore is quite tightly bound to LibSass. Every breaking change in LibSass C API will break hLibSass (either at compile-time or at runtime, depends on the change). For now, these combinations should work:

  • hLibsass 0.1.5.x with LibSass 3.3.2 (distributed with) and 3.4.3 (not every function is reexported, but there were no changes that would break hLibSass),
  • hLibsass 0.1.6.x with LibSass 3.4.3 (distributed with),
  • hLibsass 0.1.7.x with LibSass 3.5.2 (distributed with)
  • LibSass 3.5.x WILL have breaking changes and will result in runtime failures of hLibSass versions prior to (and probably compile-time failures too), see LibSass releases page for more details.

Things to consider

Libsass is C++ library with C API, so in order to use it, it is necessary to provide C++ runtime. This library is linked against libstdc++ (Windows & Linux)/libc++ (macOS) automatically, so you don't have to deal with linking process.

Known limitations

GHCi not able to load hLibSass

GHC 7 is unable to load static version of native libraries (at least some of them) and therefore it rejects loading libsass.a. On Linux, you can overcome this by switch to GHC 8 (tested with 8.0.2 with LTS Haskell 8.5) or by using shared or external (also shared) version of LibSass. On macOS, GHC 8 still rejects the library (it detects unresolver/duplicated symbols), so the only solution is to use shared/external LibSass (Homebrew version works).


Copyright (c) 2015-2018 Jakub Fijałkowski. See LICENSE for details.