На Unix:
обычно Вы запускаете cpan в Вашей оболочке:
# cpan
и тип
install Chocolate::Belgian
или в краткой форме:
cpan Chocolate::Belgian
В Windows :
при использовании ActivePerl в Windows, страница в минуту (Диспетчер пакетов Perl) имеет большую часть той же функциональности как CPAN.pm.
Пример:
# ppm
ppm> search net-smtp
ppm> install Net-SMTP-Multipart
видят , Как я устанавливаю модули Perl? в CPAN FAQ
Много дистрибутивов поставляют много модулей жемчуга как пакеты.
apt-cache search 'perl
pacman -Ss '^perl-'
dev-perl
Вы должны всегда , предпочитают их, поскольку Вы извлекаете выгоду из автоматического (безопасность) обновления и простота [1 141] удаление . Это может быть довольно хитро с сам инструмент cpan .
Для хинду существует хороший инструмент, названный g-cpan, который создает/устанавливает модуль из CPAN и создает хинду пакет ( ebuild) для Вас.
pacman -Ss '^perl-'
dev-perl
Вы должны всегда , предпочитают их, поскольку Вы извлекаете выгоду из автоматического (безопасность) обновления и простота [1 141] удаление . Это может быть довольно хитро с сам инструмент cpan .
Для хинду существует хороший инструмент, названный g-cpan, который создает/устанавливает модуль из CPAN и создает хинду пакет ( ebuild) для Вас.
"1" is equal to "1".
"0" comes before "2" (so "1040" < "12000").
"4" comes after "0" (so "1040" > "10000").
The fancy word here describing this ordering is "lexicographical order" (and sometimes "dictionary order"). In everyday language we just refer to it as "alphabetical order". What this means is that we place first an ordering on our alphabet (A
, B
, ... Z
, etc.) and then to compare two words over this alphabet we compare one character at a time until we find two non-equal characters in the same position and return the comparison between these two characters.
Example: The "natural" ordering on the alphabet { A, B, C, ..., Z }
is that A < B < C < ... < Z
. Given two words s = s_1s_2...s_m
and t = t_1t_2...t_n
we compare s_1
to t_1
. If s_1 < t_1
we say that s < t
. If s_1 > t_1
we say that s > t
. If s_1 = t_1
we recurse on the words s_2...s_m
and t_2...t_n
. For this to work we say that the empty string is less than all non-empty strings.
In the old days, before Unicode and the like, the ordering on our symbols was just the ordering for the ASCII character codes. So then we have 0 < 1 < 2 < ... < 9 < ... < A < B < C < ... Z < ... < a < b < c < ... < z
. It's more complicated in the days of Unicode, but the same principle applies.
Now, what all this means is that if we want to compare 1040
and 12000
we would use the following:
1040
compare to 12000
is equal to 040
compare to 2000
which gives 040 < 2000
because 0 < 2
so that, finally, 1040 < 12000
.
1040
compare to 10000
is equal to 040
compare to 0000
is equal to 40
compare to 000
which gives 40 > 000
because 4 > 0
so that, finally, 1040 > 10000
.
The key here is that these are strings and do not have a numerical meaning; they are merely symbols and we have a certain ordering on our symbols. That is, we could achieve exactly the same answer if we replaced 0
by A
, 1
by B
, ..., and 9
by J
and said that A < B < C < ... < J
. (In this case we would be comparing BAEA
to BAAAA
and BAEA
to BCAAA
. )
The strings are compared, one character at a time, from left to right:
10000
1040
12000
There's nothing wrong with comparing strings of different lengths.
It compares the "numbers" on a character by character basis. In the first case, "1" == "1", but then "0" < "2" in ASCII (and as an integer) so it returns true.
In the second case, 1==1, 0==0, but 4 > 0, so it returns false.
And there's nothing wrong with comparing strings of a different length... but you should use the appropriate string comparison method.
You're experiencing lexicographical ordering.
There are some generalized algorithms for this ordering in the book Elements of Programming. Search for the word lexicographical
.
In C, string comparisons are done character by character. In the first case, the first characters of the stings are equal, so it comes down to the second character: '0' is < '2', so "1040" < "12000". In the second case, the first two characters of the strings are equal, so the third character is the basis -- '4' > '0', so "1040" > "10000".
If you want them compared as numbers, you'll need to convert them to numbers first, then do the comparison.
It compares each character since you are comparing strings. If you wish to compare the numbers, then make them a numerical type.
"10000" <= "1040" <= "12000" in the same way that "fabricate" <= "fact" <= "foolish".
To expand on the John P's answer, think of the strings as words, and read them left-to-right.
To look at it another way,
BAEA would come before BCAAA but after BAAAA
Как насчет того, чтобы сделать их одинаковой длины?
Что бы объединить числа и альфа
1040 становится 01040
01040 < 12000 теперь это имеет смысл
возможно, именно поэтому он посчитал неправильным сравнивать строки разной длины Если строки являются числами, они должны иметь одинаковую длину