• Rubiks Race Re-rolling

    My son recently picked up a copy of Rubiks Race, a kids’ board game that’s essentially a slide puzzle turned into a two-player showdown. You first generate a random target pattern by rolling nine six-coloured dice in a little container, and then each player slides their tiles around to match the pattern. Sometimes the target pattern is invalid – when it has 5 or more of the same colour – but how often exactly?

  • Greater-than Sudoku in MiniZinc

    Greater-than Sudoku is like an ordinary Sudoku puzzle, but the number clues are replaced with less-than and greater-than relations.

    Sergii Dymchenko showed how to solve it with ECLiPSe, and Hakan Kjellerstrand translated that to Picat, so I couldn’t resist trying to model it in MiniZinc.

  • Template Haskell for faster linear interpolation

    An application I’m writing requires a lot of linear interpolation of a function. There’s so much of it, in fact, that it was the biggest single contributor to the running time. In this article I show how I used Template Haskell to make it much faster and cut the overall running time of the application by about a third.

  • Diagrams + Cairo + Gtk + Mouse picking

    Diagrams is the best library for drawing diagrams in Haskell. But can it be used as part of a user interface so you can interact with parts of a diagram?

    The answer is: yes.

  • Sequence, full laziness, space leak

    Recently I was surprised by the behaviour of a Haskell program I wrote. This simple example demonstrates the problem:

  • Diagrams internals

    This article covers a small part of the internals of Diagrams, a Haskell library for drawing static and animated diagrams. In particular, I give an overview of how a diagram is represented, how paths work, and how attributes are applied to diagrams. The Diagrams library has a lot in it, so not everything can be covered in great detail in such a short article.

  • Automatic Minesweeper Solver

    The game Minesweeper is a fun diversion, but even more fun would be to get the computer to solve it for us. I’ve written a basic solver for the version of Minesweeper from Simon Tatham’s excellent Portable Puzzle Collection, called Mines. My solver interacts with the game just like a human player would: by reading the screen’s contents and moving and clicking the mouse.

    Here is a video of the solver in action.

  • Solving Hexiom using Constraint Programming

    A few months ago, Laurent Vaucher wrote a couple of articles (starting with this one) about solving the puzzle game Hexiom using search algorithms and hand-crafted constraint propagation. It looked like an interesting puzzle, and I was curious about how well a generic constraint solver would perform and how to model the problem. Here I describe how I used MiniZinc and Gecode to tackle it.

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