Inside 736-131

Existential Pontification and Generalized Abstract Digressions


Try Backpack: ghc --backpack

Backpack, a new system for mix-in packages in Haskell, has landed in GHC HEAD. This means that it has become a lot easier to try Backpack out: you just need a nightly build of GHC. Here is a step-by-step guide to get you started. Download a GHC nightly Get a nightly build of GHC. If […]

  • October 10, 2016

The Base of a String Theory for Haskell

One of the early posts from this blog, from 2010, was on the subject of how to pick your string library in Haskell. Half a decade later, the Haskell ecosystem is still largely in the same situation as it was half a decade ago, where most of the boot libraries shipped with GHC (e.g., base) […]

  • September 7, 2016

Backpack and separate compilation

When building a module system which supports parametrizing code over multiple implementations (i.e., functors), you run into an important implementation question: how do you compile said parametric code? In existing language implementations are three major schools of thought: The separate compilation school says that you should compile your functors independently of their implementations. This school […]

  • September 1, 2016

cabal new-build is a package manager

An old article I occasionally see cited today is Repeat after me: "Cabal is not a Package Manager". Many of the complaints don't apply to cabal-install 1.24's new Nix-style local builds. Let's set the record straight. Fact: cabal new-build doesn't handle non-Haskell dependencies OK, so this is one thing that hasn't changed since Ivan's article. […]

  • August 29, 2016

What Template Haskell gets wrong and Racket gets right

Why are macros in Haskell terrible, but macros in Racket great? There are certainly many small problems with GHC's Template Haskell support, but I would say that there is one fundamental design point which Racket got right and Haskell got wrong: Template Haskell does not sufficiently distinguish between compile-time and run-time phases. Confusion between these […]

  • July 18, 2016

Announcing cabal new-build: Nix-style local builds

cabal new-build, also known as “Nix-style local builds”, is a new command inspired by Nix that comes with cabal-install 1.24. Nix-style local builds combine the best of non-sandboxed and sandboxed Cabal: Like sandboxed Cabal today, we build sets of independent local packages deterministically and independent of any global state. new-build will never tell you that […]

  • May 2, 2016

ghc-shake: Reimplementing ghc -​-make

ghc --make is a useful mode in GHC which automatically determines what modules need to be compiled and compiles them for you. Not only is it a convenient way of building Haskell projects, its single-threaded performance is good too, by reusing the work of reading and deserializing external interface files. However, the are a number […]

  • January 7, 2016

What is Stateless User Interface?

The essence of stateless user interface is that actions you take with a program should not depend on implicit state. Stateless interfaces are easier to understand, because an invocation of a command with some arguments will always do the same thing, whereas in a stateful interface, the command may do some different than it did […]

  • November 27, 2015

Is no-reinstall Cabal coming to GHC 8.0?

You might be wondering: with the beta release of no-reinstall Cabal, is this functionality be coming to GHC 8.0? (Or even a new release of Cabal, since the no-reinstall feature works with GHC 7.10). Unfortunately, there is a split among the Cabal developers over whether or not the actual no-reinstall behavior should go into Cabal […]

  • September 18, 2015

Help us beta test “no-reinstall Cabal”

Over this summer, Vishal Agrawal has been working on a GSoC project to move Cabal to more Nix-like package management system. More simply, he is working to make it so that you'll never get one of these errors from cabal-install again: Resolving dependencies... In order, the following would be installed: directory- (reinstall) changes: time-1.4.2 -> […]

  • August 29, 2015