Portable pleasure

This spring, I got convinced I needed a netbook. Essentially, I'm a satisfied Apple user (mostly). However, I needed a portable machine to work with. Work means coding. No code, no work. Moreover, I was curious of the new Windows 7 operating system and I also wanted to check Linux progresses as a desktop OS. I don't consider myself an Apple zealot: no Apple netbook, does not mean no netbook at all. I think Virtual Machines are a great tool. However, I don't really relate with virtual os's. I don't customize them. I just use them in order to perform some given tasks (e.g., testing). I thought that using Linux and Windows as primary operating systems when I only had the netbook was a great way to try them. I was pretty sure I could work with Linux (and I was confident I could overcome every installation issue that would have faced). I bought an Asus EEE 1005PE with 14h of autonomy declared. Other specs were completely uninteresting to me. CPU, RAM. I didn't give a fuck. If I need power, I've got a Mac Pro. If I need portable power, I have a Mac Book Pro. The EEE has plenty of HD space, and comes already partitioned (which means installing Linux is easy and you retain the EEE auto-reinstal clean windows capabilities). Should I need more ram, I could buy it. Ubuntu 10.4 is a pleasant surprise: I have never seen such a nice DE in a non Apple OS. The desktop is nice, the apps work great. NetworkManager does not suck anymore, some Ubuntu specific apps are very nice. It is rather pleasurable to work with (even if I don't use the netbook remix variant). Of course, some apps are completely lacking. However, I need it to code, write docs, email, browse... chat. Good. Windows was both a nice surprise and a disappointment. Compared to other MS OS's it is a nice surprise. It is fast, small, easy to use. Compared to what I read about Windows 7 it is a delusion: I think that Ubuntu is way nicer. However, I need some MS applications and that's it. With a little bit of work I installed everything I needed and I have got a nice working system. Unfortunately, Windows seems to slow down progressively and I don't understand why (I stopped installing stuff, I don't think that could be the cause). Hardware support is excellent both with Windows and with Ubuntu. Battery life lasts longer with Windows. I think about 12 hours of effective light work, wireless on. Ubuntu is probably around 9, which is sufficient for my goals.

Location:Via Montebello,Parma,Italy

The power of the power of the power...

Though I really don’t particularly like writing about hardware in my blog, I provide some updates on my current hardware situation. Some years ago, I wrote a short series of blog posts about my iMac. That was a first series machine and I criticized lack of support for scientific software. This is partly related to GMP not being too much collaborative (as it appears they did not have intel macs, bac in the day).

Of course those problems have been entirely solved quite soon. I suppose that by the end of the year they were no more and the faster intel chips were just the right choice for everyone. A couple of years after those events I bought a MacBook Pro 15” laptop and that became my main work machine. Among the things I really liked best about the intel processor (and all the lovely virtualization software packets out there) was that I could run Linux in a virtual machine. Since I did not stop working on a certain “almost-linux-only” project, that was really good (and saved me from ugly partitioning). Although I had a Parallels license (which I used on the iMac), I preferred to use the simpler VirtualBox. Back in the day, Parallels did not support Linux exceptionally well and I could just live with the free VB. And that is the machine I used (along with the iMac) for my M.Sc. dissertation.

4 years after i first turned it on, my iMac blew off. Well, not literally. I suppose I can fix it, however, I chose to buy a new Mac. This time it is a MacPro. Essentially, I hated that if I thrashed my iMac (because of other damages) I could not save the monitor. So I chose a monitor-less computer. Essentially the thing is powerful. It is extremely evident when encoding my CDs into mp3’s. I don’t do much video editing.

Nonetheless, Parallels is completely capable of sucking all the resources. I had to stop using it, since the MP became useless. I suppose it may be related to having only 3 GB, even though the iMac had only 2. If I will need a virtualization software, I suppose I’ll go with VMWare or VirtualBox. But… that is not the last machine I bought.

Glad I chose Blogger

This new command line thing is awesome.

Probably I would have regretted if I chose another blog service.
This also makes me think writing the crappy little blogging application for Linux should be pretty easy. :)

Prolog Homoiconicity

Although when talking about homoiconicity the first language that springs into mind is Lisp (or a Lisp dialect), Prolog is a completely homoiconic language. In Prolog everything is a term. Variables, atoms, numbers are terms. And everything else is a compound term: e.g., foo(a, b) is a term. Lists are the main data structure of Prolog, and a list is a term as well. In fact a Prolog list is i) the empty list []; ii) a term '.'(a, b), where a is a term and b is a list or a variable. We say that a compound term foo(x, y) has functor foo and arity 2. Clauses (the prolog equivalent of "functions") are represented as terms whose main functor is :-, their head is a prolog term and their body is a prolog term as well. Moreover, the read predicate reads from file (or standard input) some prolog predicates. E.g., this simple Prolog program reads a Prolog program into memory (and the program is represented as a list of prolog terms):

read_all([Predicate|T]) :-
	read(Predicate),
	Predicate \== end_of_file, !,
	read_all(T).
read_all([]).

read_file(File, L) :-
	see(File), read_all(L), seen.

If we call read_file to read "read_file.pl" (spaces added by me):

?- read_file('read_all.pl', L).
L = [(read_all([_A|_B]):-read(_A),_A\==end_of_file,!,read_all(_B)),
     read_all([]),
     (read_file(_C,_D):-see(_C),read_all(_D),seen)] ? y

The display predicate some prolog interpreters provide gives us more insight on internal representation of terms. We call it on just one rule in order not to clutter the output with list representations:

?- read_file('read_all.pl', [H|_]), display(H).
:-(read_all(.(_932,_952)),,(read(_932),,(\==(_932,end_of_file),,(!,read_all(_952)))))

And here on the full program (notice... lists are "consed" with the '.' functor):

?- read_file('read_all.pl', L), display(L).
.(:-(read_all(.(_900,_920)),,(read(_900),,(\==(_900,end_of_file),,(!,read_all(_920))))),.(read_all([]),.(:-(read_file(_1410,_1430),,(see(_1410),,(read_all(_1430),seen))),[])))

Indeed, infix operators have been placed in prefix form like every other predicate (indeed, they are not special, just a parsing trick). Another "useful" predicate (not standard) is portray_clause/1, in order to do some "pretty-printing":

?- read_file('read_all.pl', [H|_]), portray_clause(H).
read_all([A|B]) :-
        read(A),
        A\==end_of_file, !,
        read_all(B).

The assert family of predicates can “store” into the Prolog database facts (this is very common, in fact, memoization is often implemented this way) and rules (this is done less frequently – and there may be a slight efficiency penality [CHECK]). Thus we can manipulate terms (indeed that is what Prolog is about) and load them as programs. Notice that I showed the read predicate only to show that “standard” Prolog programs are represented that way, but it is not necessary at all to use programs saved in files.

4 ?- assert((foo(X) :- bar(X), \+ baz(X))).
true.

5 ?- assert(bar(1)), assert(bar(2)), assert(baz(2)).
true.

6 ?- foo(X).
X = 1 .

PDF and other tragicomical histories

Today I had the unlucky task of creating a PDF from a Word document we wrote.
In fact, I did not think the thing would have gotten tricky (ah, how naive!). Word 2007 has a nice "save to PDF" menu item and I thought I could use that to solve my problem. Luckily enough, I double checked the generated PDF on the Mac. And, apparently, all the bold fonts were substituted with another font. I already mentioned this in a post earlier today.

This is completely illogical since the font was Times New Roman and I have Word on the Mac as well, which would install a lot of additional fonts, even if TNR was not that standard. So I searched for a Windows PDF creator (which, by the way both OS X and Linux-based desktop programs have). I found a bunch of them, some commercial, some free, some open source. My choice was PDFCreator.

Some reasons are: i) it is free as in free beer, ii) it is free as in free speech, iii) had no ads, iv) is based on the same softwares I happily used with Linux. Of course, reason i) was paramount: I had no intention to buy a stinking PDF creator for Windows unless it is absolutely necessary (which may be). The other three reasons have to be considered together: I searched google for suggestions, but I had no clue on which one was supposed to be better.

Usually the only problem with open source software is lack of support/user friendliness. However, that was not the case of PDFCreator. Unfortunately, for reasons beyond my comprehension, the generated pdf completely screws[0] a TIFF picture I put in the document. The same picture is perfectly fine in the PDF generated with word built-in generator. I tried to include in word a PDF, but that did not work either (the PDF was linked, but not visible -- nor printable --). Amazingly, Word for Mac is capable of using PDF image files, IIRC.

Perhaps, I should have tried more generators. I went home, opened Word for Mac, double checked that the formatting was fine (which was not, but I could fix it in little time) and simply printed to PDF. The PDF is perfect. This goes under: how to completely waste a Monday morning.

Footnotes

[0] This is a technical term, essentially it looked like it had low resolution

A matter of homoiconicity

Somewhere around the late sixties the term “homoiconicity” has been introduced in the computer science community. In fact, the term was older and dates to the 1960, at least according to Wikipedia. Strangely enough, I did not find traces of the term homoiconic or homoiconicity in McIllroy [1]. I was not unable to recover the full text of the paper on TRAC [2]. However, widespread use of the term is due to McKay (along for the very idea of object oriented programming and a good deal of criticism on Lisp – perhaps I will look for some opinions of famous lispers on Smalltalk to make things even) in his Ph.D. dissertation.

The basic idea is simple: program is data. That is to say, the program is represented in the very same format as data. Thus, a program can manipulate programs (and even itself) in the same ways it uses for data. This is great and is the foundation for great and funny meta-programming.

Indeed, references on TRAC should make clear that a structured representation of programs is not needed. TRAC manipulated strings and programs where represented as strings. On the other hand, Lisp manipulates lists and a program is a list. It is quite rare in a discussion on programming languages with a lisper that he does not use the term “homoiconic” somewhere in the discussion, usually before becoming condescending (a proof of this is being developed actively – no trolls have been harmed during the experimentations).

What I find extremely interesting is that this great property was simply obvious in theoretical models. Universal Turing Machines and primitive functions need an enumeration of programs (functions, respectively) in order to manipulate such objects. If such enumeration was not possible, most computer science would not have been created.

The von Neumann architecture also relies heavily on instructions being represented as numbers and stored along with data. It’s a bit of a pity that this properties have not been naturally ported to programming languages (except from Lisp and some others).

Indeed, we all agree that homoiconicity is a great property in programming languages. In fact, I often find frustrating complete lack of it (e.g., Java is completely not homoiconic, since its main data structure is the Object but Java programs are not even near to being objects – ok, you can always call the compiler get an AST… but this is not what the whole thing is about). Other languages have limited support for it.

In Python functions and classes (and objects) are available when compiling a module. The whole decorator concept, for example, relies on the fact that functions are objects and can be passed as such at compile time. Very powerful meta-programming techniques in Python rely on “program” manipulation, where programs are represented as classes and functions (and not syntactically, like in Lisp). This makes some kind of manipulation very hard (without resorting to byte-code manipulation – and then the same objection with the java compiler/AST thing applies – or to basic string manipulation, which I would not consider as a symptom of homoiconicity, since strings are not “the main data” in Python). However, I would not rule Python out of the bunch of homoiconic languages, either. Perhaps “partially homoiconic” applies? Or perhaps do we need better built in tools to manipulate classes and functions in Python to qualify for the full homoiconic(tm) certification from old lisp hackers[3]?

References

1. McIlroy, M. D. 1960. Macro instruction extensions of compiler languages. Commun. ACM 3, 4 (Apr. 1960), 214-220. DOI
2. MOOERS, C.N. TRAC, a text handling language. Proc. ACM 20th Nat. Conf. Cleveland, Aug. 1965, pp. 229-246.
3. Not meant to be offensive… perhaps old could be replaced with ancient?

Using word to write...

Using word to write articles is a rather perverted art. E.g., why are the "regular expression" different from every other syntax I met and there are two different syntaxes depending whether you are using jolly characters or not?

Why is the bibliographic tools such a joke that almost everybody does it by hand (and, moreover, many conferences explicitly tell you to do it by hand? and the W2007 implementation is not compatible with W2003 – at least that is the opinion of W2007 on that matter)

And using images is a PITA. But that is a PITA with Latex as well. Last but not least, I have yet to understand why a PDF created with word for windows visualize bold characters (I'm following the IEEE template, so changing the font is not an option... besides, it's times new roman) with a *different* non-bold font when opened on the Mac. If it were not such a standard font I would have said it's a matter of not including the font.

Yet another C++ unit-testing library (nano-unit++)

http://bitbucket.org/rik0/nano-unit/
Goals: be easy to use, be easy to install
Right now, it does less than needed. However, I plan to add features as I need them. Besides, I want to make it as DRY as C++ allows, even at the cost of fighting with template metaprogramming.
However, I hope I won't need boost, as it would be a rather important and expensive dependency.