Perl. Оператор диапазона

wwoland

Дайте плз пример использования сабжа в скалярном контексте

ava3443

тоже интересно стало
гугл нашёл немало примеров
вот, например:
http://www.perlmonks.org/?node_id=377450
оно?

wwoland

Ну да, похоже он только для файлов применяется.
Если так, то более-менее понятно, я то думал он в другом контексте(не в смысле скаляр/список может применяться

Bibi

буквально вчера на лоре в комментах про перл проскочила ссылка, где мужик сильно ругался на эту доку:

Range Operator

--------------



Binary ".." is the range operator, which is really two different operators

depending on the context.  In a list context, it returns an array of values

counting (by ones) from the left value to the right value.  This is useful for

writing `for (1..10)' loops and for doing slice operations on arrays.  Be aware

that under the current implementation, a temporary array is created, so you'll

burn a lot of memory if you write something like this:



     for (1 .. 1_000_000) {

        # code

     } 



In a scalar context, ".." returns a boolean value.  The operator is bistable,

like a flip-flop, and emulates the line-range (comma) operator of *sed*, *awk*,

and various editors.  Each ".." operator maintains its own boolean state.  It

is false as long as its left operand is false.  Once the left operand is true,

the range operator stays true until the right operand is true, *AFTER* which

the range operator becomes false again.  (It doesn't become false till the next

time the range operator is evaluated.  It can test the right operand and become

false on the same evaluation it became true (as in *awk* but it still returns

true once.  If you don't want it to test the right operand till the next

evaluation (as in *sed* use three dots ("...") instead of two.)  The right

operand is not evaluated while the operator is in the "false" state, and the

left operand is not evaluated while the operator is in the "true" state.  The

precedence is a little lower than || and &&.  The value returned is either the

null string for false, or a sequence number (beginning with 1) for true.  The

sequence number is reset for each range encountered.  The final sequence number

in a range has the string "E0" appended to it, which doesn't affect its numeric

value, but gives you something to search for if you want to exclude the

endpoint.  You can exclude the beginning point by waiting for the sequence

number to be greater than 1.  If either operand of scalar ".." is a numeric

literal, that operand is implicitly compared to the $. variable, the current

line number.  Examples:



As a scalar operator:



     if (101 .. 200) { print; } # print 2nd hundred lines

     next line if (1 .. /^$/);  # skip header lines

     s/^/> / if (/^$/ .. eof;        # quote body



As a list operator:



     for (101 .. 200) { print; }        # print $_ 100 times

     @foo = @foo[$[ .. $#foo];  # an expensive no-op

     @foo = @foo[$#foo-4 .. $#foo];     # slice last 5 items



The range operator (in a list context) makes use of the magical autoincrement

algorithm if the operaands are strings.  You can say



     @alphabet = ('A' .. 'Z');



to get all the letters of the alphabet, or



     $heigit = (0 .. 9, 'a' .. 'f')[$num & 15];



to get a hexadecimal digit, or



     @z2 = ('01' .. '31');  print $z2[$mday];



to get dates with leading zeros.  If the final value specified is not in the

sequence that the magical increment would produce, the sequence goes until the

next value would be longer than the final value specified.

wwoland

Это не дока, это Кэмэл бук!
После прочтения как раз этого места и возник вопрос!