Inside 206-105

Existential Pontification and Generalized Abstract Digressions

September, 2013

If you’re using lift, you’re doing it wrong (probably)

David Darais asked me to make this public service announcement: If you're using lift, you're doing it wrong. This request was prompted by several talks at ICFP about alternatives to monad transformers in Haskell, which all began their talk with the motivation, "Everyone hates lifting their operations up the monad stack; therefore, we need another […]

Of Monadic Fixpoints and Heap Offsets

Here at ICFP, sometimes the so-called “hallway track” is sometimes just as important as the ordinary track. Johan Tibell was wanting to avoid an out-of-line call to allocate function in GHC when a small array of statically known size was allocated. But he found the way that GHC's new code generator handles heap allocation a […]

Induction and logical relations

Logical relations are a proof technique which allow you to prove things such as normalization (all programs terminate) and program equivalence (these two programs are observationally equivalent under all program contexts). If you haven't ever encountered these before, I highly recommend Amal Ahmed's OPLSS lectures on the subject; you can find videos and notes from […]

Cost semantics for STG in modern GHC

One of the problems with academic publishing is that it’s hard to keep old papers up-to-date. This is the certainly case for this 1995 Sansom paper on profiling non-strict, higher-order functional languages. While the basic ideas of the paper still hold, the actual implementation of cost centers in GHC has changed quite a bit, perhaps […]