ezyang’s blog

the arc of software bends towards understanding

September, 2012

Template project for GHC plugins

There is a bit of scaffolding involved with making Core-to-Core transforming GHC plugins, so I made a little project, based off of Max Bolingbroke’s examples, which is a nice, clean template project which you can use to create your own GHC plugins. In particular, it has documentation and pointers to the GHC source as well […]

  • September 28, 2012

“This is really the End.”

Done. This adjective rarely describes any sort of software project—there are always more bugs to fix, more features to add. But on September 20th, early one afternoon in France, Georges Gonthier did just that: he slotted in the last component of a six year project, with the laconic commit message, "This is really the End." […]

  • September 24, 2012

Unintuitive facts about Safe Haskell

Safe Haskell is a new language pragma for GHC which allows you to run untrusted code on top of a trusted code base. There are some common misconceptions about how Safe Haskell works in practice. In this post, I’d like to help correct some of these misunderstandings. [system 'rm -Rf /' :: IO ExitCode] is […]

  • September 17, 2012

The Y Combinator and strict positivity

One of the most mind-bending features of the untyped lambda calculus is the fixed-point combinator, which is a function fix with the property that fix f == f (fix f). Writing these combinators requires nothing besides lambdas; one of the most famous of which is the Y combinator λf.(λx.f (x x)) (λx.f (x x)). Now, […]

  • September 12, 2012