On Giants' Shoulders

Git and RSA identities

2012-02-06T10:36:00.000+01:00

Here is the solution I found to be able to use git with a different RSA identity than the rsa_id default one.

My repo on github is logback-android and my user account is espinielli.
I did generate an SSH key as per github help and named it github_rsa:
$ ssh-keygen -t rsa -C "your_email@youremail.com" -f github_rsa

I then added the following section in ~/.ssh/config

# github for espinielli
Host github
HostName github.com
User espinielli
IdentityFile /Users/espin/.ssh/github_rsa

From within the repo directory (I cloned it before via http):
$ git remote add gh ssh://git@github.com/espinielli/logback-android.git

And finally I am able to use it like this:
$ git push gh master

LaTeX on Blogger again

2012-01-20T16:30:00.001+01:00

My previous post about LaTeX on Blogger reported that the solution described there did not work anymore...
Now I found a new solution based on mathjax.

So let's try it straight away with inline math, like the great equation $e^{-2\pi}$, and with displayed math like the following:
\[ \left [ - \frac{\hbar^2}{2 m} \frac{\partial^2}{\partial x^2} + V \right ] \Psi
= i \hbar \frac{\partial}{\partial t} \Psi \]

(What was) Croquet is maybe still alive

2011-03-26T21:15:00.000+01:00

It seems there is still some hope to see Croquet (or, OpenCobalt which took off from where Croquet stopped) alive and based on latest Squeak and more importantly using Cog VM.
Matthew Fulmer reports it here.

The potentials are magical as explained by Howard Stearns.

Investigating Pier

2010-10-31T16:22:00.002+01:00

I have been playing around with Pier.
It is fun, especially when you can extend it to show LaTeX formulae (this is still work in progress given I am using the js from MathJax [even if forbidden], but hey I wanted a proof of concept!)

I will try to complete it: whatch out 'Beautiful Math for Pier' on squeaksource.

LaTeX on Blogger

2009-11-11T15:39:00.006+01:00

An inline snippet of LaTeX $e^{\pi i}+1=0\$ in blogger (from http://watchmath.com/vlog/?p=438 but it now, Oct 2010, shows crap!).

You can as well have it in display style:
\[e^{\pi i}+1=0\\]

Geomapping: what a wonderful world!

2009-10-27T23:56:00.003+01:00

Suppose you have a set of lat/lon points, where do you find out their elevation?
Simple, let say you have the following coordinates (a cross in concrete on the top of the hill in front of my parents' place):
45.469678, 10.970527 (I got these from 'Get Directions from here' in google maps)
Then call a USGS' web service from the URL below.
It says
getElevation
for Latitude 45.46 --> Y_Value=45.469678
for Longitude 10.97 --> X_Value=10.970527
return result in meters --> Elevation_Units=METERS
use the best survey available --> Source_Layer=-1
not other additional info --> Elevation_Only=true

http://gisdata.usgs.gov/xmlwebservices2/elevation_service.asmx/getElevation?Y_Value=45.469678&X_Value=10.970527&Elevation_Units=METERS&Source_Layer=-1&Elevation_Only=true

Why would you want elevations?

To plot an elevation chart of a bike or hiking tour.

Amazing what you can find around...

(This was inspired by http://econym.org.uk/gmap/altitude.htm)

PyCalCal is out!

2009-10-26T15:44:00.002+01:00

I finally set to put PyCalCal out in the open.
I will need to finalize and perfect it but that is a good starting point.
I also added a demo web app using it.

My idea is for PyCalCal to be used as a Python library and as such use it to provide calendrica calculations as web services.
Stay tuned if you are interested.

Giants' Shoulders in music

2009-07-28T23:56:00.002+02:00

A nice song about a great Giant, Galileo, by the Chromatics.
Read text and listen to music, here

Scons and noweb

2009-06-14T11:21:00.006+02:00

I was curious to see how I could integrate noweb and Scons.

You can download my little Sconstruct for this, Sconstruct.example. It defines two builders. NoWeave is used to produce TeX or LaTeX documents, while NoTangle extracts the non-document artefacts, i.e. programs, config files, scripts ... It also includes productions for generating a sample program about Ackermann function:


ackdoc  = env.NoWeave('ack.tex', 'ack.nw')
ackcode = env.NoTangle('ack.py', 'ack.nw')
acktest = env.NoTangle('ackTest.py', 'ack.nw')

The noweb source is ack.nw and the companion BibTeX file is ack.bib

It contains the doc chunks describing the function, the source code chunck for the relevant Python code and the code chunk for the unit test

You can try it out executing

$ scons -f Sconstruct.example

You will get the following artefacts, ack.py, ack.tex, ackTest.py and ack.pdf

Remember to run BibTeX first...

LaTeX, Python and Literate Programming

2009-02-24T10:45:00.001+01:00

In my spare time (a couple of hours per weekend...!) I am implementing calcal, a Python version of calendrica-3.0.cl, the Common Lisp implementation of the calendars from N. Dershowitz, E. M. Reingold Calendrical Calculations, 3rd Edition. (In case you are interested you can find a preview in my google page.)
At some point I decided to go Literate [Programming] using noweb. This is an experiment in the experiment but so far it has been a good choice because I can define all I need in the same place and generate documentation, source code (Python, shell scripts ...) from the same source.
I also found something interesting (on a now disappeared blog ttp://usefreetools.blogspot.com): executing Python from within LaTex! I could use it to avoid to hardcode results in my doc and just calculate them on the fly...
The same blog was showing how to build LaTeX docs using SCons: I will defenitly use it; my Makefile isn't that great nor easy to mantain.

My Giants

2009-02-23T14:51:00.005+01:00

I am probably too selective, anyway my models for computer science/software engineering (one of them would disagree on both definitions) are just two: Donald E. Knuth and Alan Kay.
The first one continues to surprise me with the depth, clarity and joy of his works: from TeX (well, I use LaTex but it does not exist without TeX) to The Art of Computer Programming to Literate Programming.
About the latter, I was one of the blessed to be present to his Turing Award Lecture: he shocked me to the point I had two sleepless nights so angry I was about having wasted so much time in useless (computer) matters! After that I have been studying and using a lot of what he wrote and presented from Squeak to Croquet to the Burroughs B5000 and stack computers to his recent line of exploration and the proposal to NSF about reinventing programming (PDF).