POZOR: Cache na vyse uvedenych souradnicich
nenajdete!! Ty pouze smeruji na jednu Perl-u prazske
architektury
.
POZOR: 16.8.2009 doslo ke zmene umisteni finalky (a hintu) - nyni
je nutno pridat k vypocitane souradnici N
ctyri tisiciny!!!!
Perl je zajimavy programovaci jazyk, ktery vytvoril Larry
Wall v roce 1987. Jedna se o takzvany interpret, coz znamena, ze se
vysledny program nepreklada, ale interpretuje radek po radku
podobne jako u Basicu.
Perl je dodnes velice popularni treba pri tvorbe CGI skriptu ci
zpracovani dat. Je vhodny pro reseni malych programku (utilit) ale
i velkych a rozsahlych projektu.
K nejvetsim vyhodam jazyka Perl patri to, ze umoznuje rychly
vyvoj programu bez nutnosti kompilace a linkovani, nabizi spoustu
jiz hotovych knihoven a modulu vcetne napojeni na nejrozsirenejsi
databazove systemy, snadnou praci s textem a znackovacimi jazyky
(XML, HTML…). K casto pouzivanym metodam pro praci s textem slouzi
velice efektivni regularnimi vyrazy, kterymi se na CC#7
budeme krome Perlu zabyvat.
Ucelem teto kesky neni vas naucit programovani v jazyce Perl,
ale ukazat Vam, jake moznosti prace s textem nabizeji regularni
vyrazy (RE - Regular Expressions), a jak snadno lze s daty s jejich
pomoci manipulovat. RE se pouzivaji i v rade jinych jazyku nebo
aplikaci. Jazyk Perl jsem vybral proto, ze je prave pro nej pouziti
RE charakteristicke. Pomoci RE je mozno jednoduchym zpusobem
ziskavat z textovych dat udaje a pretvaret je do jine podoby.
Co je vlastne regularni vyraz? Je to jednoduse retezec, ktery
popisuje urcity vzorek. S jejich jednoduchou formou jste se
pravdepodobne setkali - napriklad prikaz dir *.* vypise vsechny
soubory v danem adresari, znak '*' zde funguje jako metaznak
s vyznamem 'libovolny pocet libovolnych znaku'. Jake dalsi
takove metaznaky se nam pri reseni CC#7 budou hodit?
| vyraz |
vyhovuje |
priklad |
poznamka |
| znak |
libovolny znak |
r |
najde 'r' ve slove Perl |
| . |
libovolný znak (krome noveho
radku) |
. |
najde 'P' ve slove Perl |
| * |
0 ci vice libovolnych znaku |
P*l |
najde 'er' ve slove Perl |
| + |
1 ci vice libovolnych znaku |
P+ |
najde 'erl' ve slove Perl |
| ? |
0 ci 1 libovolny znak |
P? |
najde 'e' ve slove Perl |
| [znaky] |
jeden z uvedenych znaku |
[0-9] |
libovolna cislice |
| [^znaky] |
libovolny znak krome uvedenych |
[^0-9] |
libovolny znak krome
cislic |
| \x |
vyradí/zapne vyznam metaznaku x |
\.\.\. |
znaky ... (opravdove
tecky) |
| ^ |
zacatek radku |
^Pe |
najde 'Perl' na zacatku
radku |
| $ |
konec radku |
l$ |
najde 'Perl' na konci
radku |
| {n} |
presny pocet n znaku |
.{2} |
libovolne DVA znaky ('Pe') |
| {n,} |
minimalne alespon n znaku |
.{2,} |
minimalne DVA znaky
('Perl') |
| {n,m} |
n az m znaku (vcetne) |
.{2,3} |
2-3 znaky ('Per') |
| | |
znak pro nebo |
[a|b|c] |
'a' nebo 'b' nebo 'c' |
| () |
vytvareni skupin |
|
|
Uz se vam z toho toci hlava? Nebojte, nic to neni, je to jen vec
cviku! Uvedme si par jednoduchych prikladu:
"Hello World" =~ /World/; v prvnim retezci se hleda slovo World
(a najde se)
"dilbert" =~ /^bert/; nenajde se (bert neni na zacatku radku)
/[bcr]at/; odpovida slovum 'bat, 'cat' a 'rat'
/pol[0-9]/; odpovida slovu 'pol' nasledovanym jednim
cislem
Pokud chcete pouzit misto metaznaku skutecny znak, musite pred
nej dat zpetne lomitko (napriklad misto '?' napsat '\?'), jinak se
interpretuje jako metaznak. Na druhou stranu existuji specialni
metaznaky, ktere funguji jen se zpetnym lomitkem a ktere z
normalnich znaku delaji prave zvlastni metaznak:
| \d |
cislo, tj. [0-9] |
| \s |
'obecna mezera', tedy i novy radek
atd - tj. [\ \t\r\n\f] |
| \w |
znak ve slovu, tj.
[0-9a-zA-Z_] |
| \D |
negace \d - cokoli krome cislice,
tj. [^0-9] |
| \S |
negace \s - cokoli krome 'obecne
mezery' [^\s] |
|
\W |
negace \w - cokoli krome znaku ve
slovu [^\w] |
Opet si uvedme priklad:
/\d\d:\d\d:\d\d/; # odpovida casovemu formatu hh:mm:ss
Operator s /// je vyuzivan k nahrazeni jednoho znaku
jinym. Napriklad v nasledujicim prikladu se kocka zmeni v
krysu:
$x = "I like cats and bats!";
$x =~ s/.at/rat/;
Pokud na konci prikazu pro nahrazeni nasleduje modifikator 'g',
provadi se toto nahrazeni opakovane:
$x = "I like cats and bats!";
$x =~ s/.at/rat/g;
Ted uz mame krysu nejen z kocky ale i z netopyra
!
K vytvareni skupin znaku slouzi zavorky (). Ty jsou vhodne i k
dalsimu ucelu - umoznuji prirazeni casti stringu, ktery odpovida
danemu regularnimu vyrazu, do specialnich promennych: $1,
$2, atd. Ty pak mohou byt pouzity jako normalni
promenne.
# oddel hodiny, minuty a sekundy
if ($time =~ /(\d\d):(\d\d):(\d\d)/) { # test, zda vstup odpovida
formatu hh:mm:ss
$hours = $1;
$minutes = $2;
$seconds = $3; }
Myslim si, za jako kratky uvod do jazyka Perl a RE to stacilo,
ne? Pokud si chcete precist vice, zkuste treba ceskou
Wikipedii, o regularnich vyrazech se doctete vice treba v
moc peknem serialu Pavla Satrapy.
Tak a ted mate k dispozici veskere indicie, abyste mohli vyresit
nas velmi zapeklity sedmiradkovy program
. Upozorneni: Je v nem schvalne 'zavlecena' jedna syntakticka
chyba, abyste nemohli svindlovat pomoci nejakeho stazeneho
interpretru Perl. Bud musite chybicku najit a odstranit, nebo
budete muset vypocty provadet rucne. Mnoho stesti pri lusteni i pri
hledani! Pozor - mikrocache obsahuje pouze logbook,
prineste si proto vlastni tuzku a v logu
setrete mistem - staci napsat pouze nick a datum. Kolem je casto
docela dost lidi. Cache ulozte na sve misto
presne tak, jak byla predtim. Diky!!!
#!/usr/local/bin/perl
my $string = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.*! ";
$string =~ s/(.)(.)(.)(.)(.)(.)(.)(.)/$3$7$6$1$8$5$4$2/g;
$string =~ /(^.{5})(\w)(.{4})(.)(.*)([rR])(.)(.)(.)([Y])
(.)(\d)(.)(\D)(.)(\W{2})(.)(\s)(.)(\w)(\S)/;
print "Cache Coordinates : $4$11$7$18$7$9$19$21$11$21$18";
print "$2$7$13$8$18$12$11$19$17$15$12\n";
print "Attention : since 16/08/09 add 0.004 to the North!!\n";
POZOR: 16.8.2009 doslo ke zmene umisteni finalky (a hintu) - nyni
je nutno pridat k vypocitane souradnici N
ctyri tisiciny!!!!
Perl
ATTENTION: There is no cache at given
coordinates!!.
Perl is a very interesting programming language. It was created by
Larry Wall at 1987. It is so called interpreter, which means that
the source code is not compiled but intrepreted line by line like
Basic.
Perl is very popular till today for
example in creating CGI scripts or in a data manipulation. You can
create small utilities or very large projects with Perl.
The biggest advantages of Perl are the
fast program development (without the need of compiling and
linking), there are many ready to use libraries and modules
including the connection to widely used database systems. Perl
programs can easily manipulate with the text and markup languages
(XML, HTML…). The Regular Expressions (RE) are mainly used
for this purpose. And Perl together with regular expressions will
be used to solve this CC#7 mystery cache.
I will not explain to you here how to use
the Perl or RE, you can find it out for yourself. There are many
sources about these subjects on the Internet. I can recommend you
for example this Perl Beginners Quide", RE
Quick Guide" or RE
Tutorial.
Ready to solve the Perl script above (the
last one in the Czech section)? Go on! I have a small warning
though - there is a small syntactic error inside, so it cannot be
solved mechanicaly by the program itself. You must either find the
error and remove it or to solve just by your head
. Good luck while solving or searching! Attention - microcache
contains only the logbook. You need to bring your
own pen! Also please save the space in the logbook, please
put only the date and nick there. Watch the people around.
Please put the cache exactly at the same place as
it was before. Thanks!!!
ATTENTION: At 16.8.2009 the final cache has been moved (and hint
changed) - You need to add 0.004 to the
North coordinate!!!!
Viz tez/See also:
Computer Cache #1
Computer Cache #2
Computer Cache #3
Computer Cache #4
Computer Cache #5
Computer Cache #6