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Set the root directory of a project in Emacs with dir-locals.el
Hi, and welcome to my blog. I’ll try to write here about the stuff I do, use or discover during my work as a Ph.D in Computer Science. There will hopefully be a bit of science (proof theory), some code...
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An OCaml hack: recover the abstraction of abstract types
Here is a scoop: in OCaml, your abstract types aren’t really abstract (unfortunately). This is because some magical functions in the standard library don’t respect the abstraction of data types:...
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Building terms, incrementally
Here is the first post of a series about incremental verification in programming languages. This problem has become more-or-less the main subject of my Ph.D, and this is an exercise in explaining it...
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Reversing data structures
A reversed list is not really a list anymore. It is isomorphic to a list, but it is not a list. Let me explain why. Prelude: zippers and contexts How do we define in general reversing a data structure?...
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Reverse natural deduction and get sequent calculus
This is a follow-up on my previous post. It should be readable by itself if you just take a quick peek at herds. Today, we are going to write type-checkers. And rewrite them. Again and again....
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Building terms incrementally: expressivity
A few weeks ago, I showed a very simple model for constructing and storing typed combinators incrementally. By incremental, I meant that type-checking was a sequential and iterative process: instead of...
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Strong reduction in big-steps
It has been a long while since I updated this blog, let me finally revive it with an easy but (hopefully) fun post, well ehm… at least some usable reference material! Strong reduction is the ability...
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My thesis is out!
At last! The definitive, final and comprehensive version of my thesis manuscript is out. I defended it on April 8 in Bologna, Italy, and received both titles of “Dottore di ricerca” and “Docteur” in...
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malloc() is the new gensym()
Teaching an introductory course to “compilation” this semester (actually it was called Virtual Machines, but it was really about compiling expressions to stack machines), I realized something I hadn’t...
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New draft: Proofs, upside down
There is a new draft on my web page, that should be of interest to those who enjoyed my posts about reversing data structures and the relation between natural deduction and sequent calculus. It is an...
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New draft on Normalization by Evaluation using GADTs
There is a new draft on my web page! It is called Tagless and Typeful Normalization by Evaluation using Generalized Algebraic Data Types, which is a mouthful, but only describes accurately the cool new...
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Quick, dirty and shallow definitions
Here is a quick hack. A few months ago, I advocated for pointer equality in OCaml (==) as a way to deal with fresh symbols in a toy compiler. Today, I’ll show another application of pointer equality:...
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1 ≠ 0
Learning Coq is usually an enlightening experience. I know it first-hand, it can also be a quite frustrating one, because it seems at first to involve remembering quite a lot of arbitrarily-named...
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Update on Typeful Normalization by Evaluation
In October, I publicized here a new draft on normalization by evaluation, which provoked some very helpful comments and constructive criticisms. Together with Chantal and Olivier, we thus revised the...
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Representing pattern-matching with GADTs
Here is a little programming pearl. I’ve been wanting to work on pattern-matching for a while now, and it seems like I will finally have this opportunity here at my new (academic) home, McGill....
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Big-step disjunctive normal forms
This is probably a second-semester functional programming exercise, but I found it surprisingly hard, and could not find a solution online. So at the risk of depriving a TA from a problem for its...
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Typeful disjunctive normal form
This is the answer to last post’s puzzle. I gave an algorithm to put a formula in disjunctive normal form, and suggested to prove it correct in OCaml, thanks to GADTs. My solution happens to include a...
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Escaping continuations
Beta had a funny joke at POPL last year; he said: “you exit a monad like you exit a building on fire: by running”. I recently got myself in the stressful situation of being trapped in a monad—the...
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Parametric HOAS with first-class modules
One of the first choice to make when starting the development of a compiler, or any program manipulating syntax with binders (e.g. programs with functions and variables), is how to represent these...
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