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diff --git a/doc/languages-frameworks/haskell.md b/doc/languages-frameworks/haskell.md index f16077cced4f..6d8984821741 100644 --- a/doc/languages-frameworks/haskell.md +++ b/doc/languages-frameworks/haskell.md @@ -793,6 +793,64 @@ It's important to realize, however, that most system libraries in Nix are built as shared libraries only, i.e. there is just no static library available that Cabal could link! +### Building GHC with integer-simple + +By default GHC implements the Integer type using the +[GNU Multiple Precision Arithmetic (GMP) library](https://gmplib.org/). +The implementation can be found in the +[integer-gmp](http://hackage.haskell.org/package/integer-gmp) package. + +A potential problem with this is that GMP is licensed under the +[GNU Lesser General Public License (LGPL)](http://www.gnu.org/copyleft/lesser.html), +a kind of "copyleft" license. According to the terms of the LGPL, paragraph 5, +you may distribute a program that is designed to be compiled and dynamically +linked with the library under the terms of your choice (i.e., commercially) but +if your program incorporates portions of the library, if it is linked +statically, then your program is a "derivative"--a "work based on the +library"--and according to paragraph 2, section c, you "must cause the whole of +the work to be licensed" under the terms of the LGPL (including for free). + +The LGPL licensing for GMP is a problem for the overall licensing of binary +programs compiled with GHC because most distributions (and builds) of GHC use +static libraries. (Dynamic libraries are currently distributed only for OS X.) +The LGPL licensing situation may be worse: even though +[The Glasgow Haskell Compiler License](https://www.haskell.org/ghc/license) +is essentially a "free software" license (BSD3), according to +paragraph 2 of the LGPL, GHC must be distributed under the terms of the LGPL! + +To work around these problems GHC can be build with a slower but LGPL-free +alternative implemention for Integer called +[integer-simple](http://hackage.haskell.org/package/integer-simple). + +To get a GHC compiler build with `integer-simple` instead of `integer-gmp` use +the attribute: `pkgs.haskell.compiler.integer-simple."${ghcVersion}"`. +For example: + + $ nix-build -E '(import <nixpkgs> {}).pkgs.haskell.compiler.integer-simple.ghc802' + ... + $ result/bin/ghc-pkg list | grep integer + integer-simple-0.1.1.1 + +The following command displays the complete list of GHC compilers build with `integer-simple`: + + $ nix-env -f "<nixpkgs>" -qaP -A haskell.compiler.integer-simple + haskell.compiler.integer-simple.ghc7102 ghc-7.10.2 + haskell.compiler.integer-simple.ghc7103 ghc-7.10.3 + haskell.compiler.integer-simple.ghc722 ghc-7.2.2 + haskell.compiler.integer-simple.ghc742 ghc-7.4.2 + haskell.compiler.integer-simple.ghc763 ghc-7.6.3 + haskell.compiler.integer-simple.ghc783 ghc-7.8.3 + haskell.compiler.integer-simple.ghc784 ghc-7.8.4 + haskell.compiler.integer-simple.ghc801 ghc-8.0.1 + haskell.compiler.integer-simple.ghc802 ghc-8.0.2 + haskell.compiler.integer-simple.ghcHEAD ghc-8.1.20170106 + +To get a package set supporting `integer-simple` use the attribute: +`pkgs.haskell.packages.integer-simple."${ghcVersion}"`. For example +use the following to get the `scientific` package build with `integer-simple`: + + $ nix-build -A pkgs.haskell.packages.integer-simple.ghc802.scientific + ## Other resources |