Suggested Reading: Les sciences de l’imprécis


Abraham A. Moles — Les sciences de l’imprécis — Seuil, 1990, 310 pp. ISBN 2-02-011620-0

(out of print?)

“Thinking about the vague is not vague thinking” would quite succinctly and accurately describe Moles’ thesis. The terminology used will be a bit disconcerting to the computer scientist as the vocabulary comes from the social sciences rather than the “hard” sciences. At times we feel that analogies drawn between the author’s ideas and information theory (and computer science) are almost stretched but we can quite forgive this since it nevertheless remains a very clear exposition of his thesis, that is, imprecision is not to be frown upon and is quite necessary to science and as such should be mastered rather than feared.

The text is almost grand public as it contains essential no maths.

Data Insecurity


It always amazes me to see how people put trust in their service providers. While in principle, there’s no real need to worry, careless implementation of services can really have dire consequences!

And it’s not like leaks and exploits are rare. Sometimes we hear about them, sometimes we don’t. Let’s consider these two (amongst those) I know about:

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Suggested Reading: The Common Sense of Science


Jacob Bronowski — The Common Sense of Science — Harvard University Press, 1978, 154 pp. ISBN 0-674-14651-4

(Buy at

I already knew Bronowski by the television series The Ascent of Man (broadcasted in french in the late 70s or maybe the very early 80s by Radio-Québec, now TéléQuébec). Even as a child, I was impressed by the depth of discourse of the series. Universal thinker, in The Common Sense of Science, Bronowski tells us how he conceives science and its methods as a fundamental human activity, and why it plays such an important (if misunderstood) rôle in our society. The narration follows more or less the evolution of science since the Enlightenment to our time and how it is tied to the industrial revolution.

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A matter of interpretation


In calculus 101, amongst the first things we learn, is that the derivative a function is the slope of the tangent to the function, that is, the instantaneous slope at some point on the function. We have, for some function F that the derivative f is given by:

\displaystyle\frac{\partial\:F}{\partial\:x}=\lim_{\Delta\to{}0} \frac{F(x+\Delta)-F(x)}{(x+\Delta)-x}=\lim_{\Delta\to{}0}\frac{F(x+\Delta)-F(x)}{\Delta}=f

So the formulation looks like a slope, and it is taught that it is a slope as well; all the concepts surrounding differentiation are expressed in terms of slopes of tangents, and that’s OK, because that’s what they are.

But suddenly, in calculus 201, we learn how to find the anti-derivative of a function, also known as the integral. But the metaphor changes completely: we’re know talking about the area under the curve. Wait. What?

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Failed Experiment


Experiments do not always work as planned. Sometimes you may invest a lot of time into a (sub)project only to get no, or only moderately interesting results. Such a (moderately) failed experiment is the topic of this week’s blog post.

Some time ago I wrote a CSV exporter for an application I was writing and, amongst the fields I needed to export, were floating point values. The application was developed under Visual Studio 2005 and I really didn’t like how VS2005’s printf function handled the formats for floats. To export values losslessly, that is, you could read back exactly what you wrote to file, I decided to use the "%e" format specifier for printf. Turned out that it was neither lossless nor minimal!

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Suggested Reading: Prisoners Dilema


William Poundstone — Prionner’s Dilema — Anchor, 1993, 294 pp. ISBN 978-0385415804

(Buy at

This book isn’t really an introduction to game theory, nor a von Neuman biography, nor a history lesson on the cold war era. Most of the book is devoted to either the cold war logic or to game theory, and little to von Neumann who, really, only serves as the main thread bringing game theory and the cold war together. Nevertheless, it’s a quite cromulent introduction, while not very math-oriented, to the fundamentals of game theory where two (or more) players are confronted and try to maximize their gain. Can or should player cooperate? If so, why?

If, like me, you think that the cold war is rather boring, just skip those part, it will still be a quite interesting read.

Wallpaper: Jardin de givre


Jardin de givre (1920×1200)

The Complex Beauty of Simplicity


As I have said before, some of my friends took the very wise decision to go back to school (that is, university) and, accordingly, they’re doing all the undergrad maths courses. As I try to help them whenever I can, I decided to ask them to solve a simple puzzle… or so I thought.

So the problem is as follows:

You have a circle of center C, radius r\geqslant{}0 and some point Z, with Z\neq{}C. Find the projection P of point Z against the circle with center C and radius r. The method should work whether Z is inside or outside the circle.

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