Friday, 29 February 2008

Lap year's WTF

Well, we all know phpBB is evil. Html code it generates makes you sick. It's a great example of spaghetti design antipattern. And it's written in PHP.

Today (it's 29th February) many phpBB by Przemo forums have blown. It's because of lap year and their "whose birthday is it" function.

Warning. Clicking link below may even make you vomit.
I'm ugly, think again

Yes, they didn't use standard date("L"), yes they did their own calculations (using sqrt?!?), and yes, they f*ck*d it badly. Awful switch full of magic numbers (hello, PHP is a junk, but it has loops and arrays) is just a minor ugliness.

Saturday, 9 February 2008

int *(*(*(*b)())[10])();

I've just read Terence Parr's post titled "How To Read C Declarations". The quoted "Golden Rule" makes reading declarations really easy even for a drunk ape, but it's one of the kind I dislike. It gives you some "magical" steps to follow (here are the same rules stated more verbosely in an awful, BASIC-ish GOTO-step-N manner) with no explanation why this way, no another.

Here is the missing explanation:

Declaration reflects how you use declared expression (how you get the value of it), so in int tab[]; tab is an array (you index it) of integers. int (*tab)[]; is a pointer to an array (you dereference it, then index). int *(tab[]); is an array of pointers — you have to index it, then dereference.

How about int *tab[]? You have to know operator precedence

It's not that hard as in looks like. In our case the rule of thumb is: "Postfix binds stronger than prefix.", so you read int *tab[] as array of pointers. "Postfix binds stronger than prefix" is the reason why you look right, then left, in "Golden rule".

Easy, isn't it? Now you know this post's title reads pointer to the function returning pointer to an array of pointers to functions returning pointers to integers. 10 is redundant in this case. (It's no 5 from here, I'm so lazy...).

Of course you'll find out that the Golden rule is an obvious result of sentences above. It's convinient to read declarations that way, but IMO it's very bad to actually think about declarations only in terms of now jump out of the parenthesis.

Friday, 1 February 2008

Vim stuff

Vim is great, but quite hard to master. My experience is that there usually is a lot of "how did you do that?" when working with another vimmer. There goes a random list of some useful commands I taught (or learned) recently:

^rX in command and insert mode.
Puts the content of X register. Typical use case: select something with * and then :%s/^r//new stuff/g

punctuation: ; and ,
repeats last tTfF motion, like everyone's favourite dot repeats last command

rectangle visual mode
^v or quadruple1 click. Often easier and faster, than macros

q. Everyone know them :help q

Jumps intro normal mode for one command. Typical usecase: editing middle of the line ^oo.

^v any_key in insert and command mode
Puts the Vim representation for that key. Useful for editing .vimrc

J in normal mode
joins current line and next line

^a ^x in normal mode
increment/decrement a number

& and \1, \2...
in to part of substitution

X11 clipboard

^p ^n and ^xlot_of_keys like ^xf

autocmds in your .vimrc
see .vimrc examples below

not a command: Wombat
My text is brilliant
My vim is pure.
I saw a Wombat.
Of that I'm sure.

You're beautiful. You're beautiful.
You're beautiful, it's true.

Some macros from my .vimrc that I found very useful:

" done with current line
inoremap <c-cr> <c-o&ht;o

autocmd FileType xml,html,xhtml,jsp,htmldjango inoremap <C-b> <Esc>"tciw<<C-o>"tp><CR></<C-o>"tp><Esc>O
autocmd FileType xml,html,xhtml,jsp,htmldjango inoremap <C-a> <Esc>"tciw<></><Esc>"tPF>"tPla
autocmd FileType xml,html,xhtml,jsp,htmldjango inoremap <C-s> <ESC>"tciw</><ESC>h"tPa<Space><Space><Left>

Side note: python syntaxfile file (at least in vim 7.0 in my SuSE) seems to be a little outdated:
autocmd FileType python syn keyword Constant True False None
autocmd FileType python syn keyword Keyword with

Meta tip:
type :help one_or_two_random_keys from time to time. prefix with i_ for insert mode stuff.

1 - yes. QUAD-ruple. Click, click, click, click. Four clicks in a row %-| . Open Office does have quadruple click too. Who uses mouse, anyway...