domingo, 7 de agosto de 2016

Setting the date of my raspberry pi

I use my rpi as an alarm clock.  It works well because you have mplayer and cron.  And that's basically it.   I used picolisp to wire everything together (and wrote a simple hack to snooze the alarm).

But one of the biggest annoyances is that Rpi doesn't have a clock on its own, so when it looses power (I disconnect it), the clock is reset, so the alarm clock won't work.. :(

As I've read "The Unix Programming Environment" lately, I'm quite fond of shell scripts now, and I got to this 4 level quoting that sets the date of my raspberry pi from my laptop.

ssh pi@192.168.1.38 -o ConnectTimeout=60 sudo date --set="\"`date '+%d %b %Y %H:%M:%S'`\""

I'm somewhere between very proud and very ashamed of that, but well... it does the job.

lunes, 25 de julio de 2016

git pre-commit blacklist

Here's a simple solution if you want git to not allow you to commit debug messages or blacklisted words.

The nice thing about the snippet is that it only counts added lines, not removed, so you can clean code with this pre-commit active, but never make it worse.


FORBIDDEN='declaim\|break'
git diff --cached | grep '^+' |  grep -n $FORBIDDEN && \
 echo "COMMIT REJECTED Found '$FORBIDDEN' references. Please remove them before commiting" &&\
 exit 1

slack -> jabber -> irc -> erc

Slack can be used though alternative gateways appart from the slack clients themselves.  They offer both jabber and irc gateways that map quite well to slack model.

I had previously used the irc gateway, and erc did the trick with no extra configuration at all. But things changed and now I only have the jabber gateway at my disposal.

The problem is that if you want to use a decent emacs client, you'll have to use bitlbee and end up mapping jabber to irc, so you can use erc/circe/rcirc (which are far better at IRC protocol than jabber.el is at xmpp)



To chat privately other peers it's a matter of /j name-of-the-buddy.  Joining rooms is not as direct, and first you have to create some 'mapping' rooms in your bitblee configuration, before being able to join them.

Whatever, here's how to integrate slack with bitlbee (and with erc)

On bitlbee buffer:
  •  chat add 0 room-name@conference.myserver-foo.xmpp.slack.com
 0 stands for the account number. 'conference' has  to be there. it's a plain string, you don't have to substitute it for anything. replace myserver-foo for your server name. room-name is the name of the chat in slack

  • chat list
This will show you the rooms available

  • /join room-name
Notice no # sign.
  • channel 4 del
4 is the chat you want to remove in case you messed up with something.

And that's it. Now you can slack from erc, and you can use all erc machinery (yes erc-robot, I'm looking at you).




jueves, 21 de julio de 2016

TIL: Embedding strings into strings in bash

In bash there's always quite a lot of quoting to be done when you're embeding commands into commands, and possibly want to interpolate some variables.


To save one quoting, there's the option to use HEREDOCS, and assign a string into a var.

lunes, 18 de julio de 2016

TIL: Remove a defined method (with defmethod) in Common Lisp

I created a defmethod for a more specialized class than the ones existed. and now I'd like to remove that method....

(remove-method #'foo (find-method #'foo '() (mapcar #'find-class '(class-of-first-specializer class-of-second-specializer))))

viernes, 15 de julio de 2016

Simple 'dsls' using strings

I'm currently reading The Unix Programming Environment (1st ed). At some point, the authors show how to make a terser version of ....

 It's not entirely clear when I saw this for the first time, I'd say I saw it in some norvig's python code (which I can't find anymore, if you know what I'm talking about comment please. I've spent too much time searching that code)


He was creating a regex from a string of whitespace separated words. something like this: "|".join(" ".split(words)) .

 I find super nice the fact that one can create abstractions on abstractions, or use data structures as intermediate stepping stones.

We (at least, myself) tend to usually think at one level of indirection. You can think of a Set implemented via an array, a hash, or a Bloom filter, but it's usually "I want the 'set' functionality, so I go and fetch an implementation of that functionality".  In those cases, they use intermediate data structures so that they can manipulate the information easily, and later convert it to some other data structure.

Another case where this thing appears is when creating Classes in Smalltalk, where you define the instance variables inside a string.

Object subclass: #Dog 
    instanceVariableNames:  
    classVariableNames:  
    poolDictionaries:  
    category: PBE-CIV 



In The Unix programming environment, at some point they write an awk script regarding calendars, and instead of:

days["Jan"]=31; nextmon["Jan"]="Feb" 

days["Feb"]=28; nextmon["Feb"]="Mar"

...


They do:

x="Jan 31 Feb 28 Mar 31 Apr 30...."

split(x, data)

for(i=1;i 24;i+=2){

  data[i]] = data[i+1]
  nextmon[data[i]] = data[i+2]

} 

domingo, 26 de junio de 2016

Functional programming in small pieces

I've been articles on reading functional programming for some time, and little by little, I think I get a bit more of the whole stuff.

I found some nice articles/tutorials, and I understood most of them (yay!)
Although I'm still fighting with some other articles like this functional pearl about using foldr to make a function to give combinations of elements. It's been too long since I started looking at it, and I still don't get it.... :/

Well, have fun, and happy hacking.