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标题: PERL两个字符串，不关心大小写 [打印本页]

作者: slwj 时间: 2014-04-01 14:52
标题: PERL两个字符串，不关心大小写
大家好，请教下，如何使用PERL来比较两个字符串，而不关心它的大小写，多谢！

作者: pitonas 时间: 2014-04-01 15:19

while(<DATA>){
my ( $one, $two) = split;
say lc($one) eq lc($two) ? 'yes' : 'no';
}
__DATA__
abc Abc
abc abd
abc ABC

复制代码

作者: huang6894 时间: 2014-04-01 15:21
回复 2# pitonas

niubility~

作者: slwj 时间: 2014-04-01 15:34

pitonas 发表于 2014-04-01 15:19

牛，不过想问下，
my ( $one, $two) = split;
，这里的split后面怎么是空的？

作者: pitonas 时间: 2014-04-01 15:38
split后面是空的 == split 空格

回复 4# slwj

作者: 黑色阳光_cu 时间: 2014-04-01 15:44

say "\L$one\E" eq "\L$two\E" ? 'yes' : 'no';

复制代码

作者: slwj 时间: 2014-04-01 15:50

pitonas 发表于 2014-04-01 15:38
split后面是空的 == split 空格

回复 4# slwj

那split是分割哪个字符串呢，$_？

作者: yestreenstars 时间: 2014-04-01 15:55
回复 7# slwj

split后面不接参数表示以空格分割$_

作者: q1208c 时间: 2014-04-02 08:27
我是真心不建议使用 $_ 这个变量.

作者: jason680 时间: 2014-04-02 09:11
回复 4# slwj

study more detail ...

$ perldoc -f split
split /PATTERN/,EXPR,LIMIT
split /PATTERN/,EXPR
split /PATTERN/
split Splits the string EXPR into a list of strings and returns that
         list. By default, empty leading fields are preserved, and empty
         trailing ones are deleted. (If all fields are empty, they are
         considered to be trailing.)
...

作者: 104359176 时间: 2014-04-02 21:00
Perl新的版本可能要废除 $_ ，代码不但是用来运行的，还是给未来的自己看的。

作者: qianyemlf 时间: 2014-04-03 12:24
lc($one) eq lc($two)
lc什么意思？

作者: jason680 时间: 2014-04-03 13:33
本帖最后由 jason680 于 2014-04-03 13:34 编辑

回复 12# qianyemlf

$ perldoc -f lc
lc EXPR
lc    Returns a lowercased version of EXPR. This is the internal
         function implementing the "\L" escape in double-quoted strings.

         If EXPR is omitted, uses $_.

$ perldoc -f uc
uc EXPR
uc    Returns an uppercased version of EXPR. This is the internal
         function implementing the "\U" escape in double-quoted strings. It
         does not attempt to do titlecase mapping on initial letters. See
         "ucfirst" for that.

         If EXPR is omitted, uses $_.

         This function behaves the same way under various pragma, such as
         in a locale, as "lc" does.

作者: seufy88 时间: 2014-04-03 13:42
回复 11# 104359176

废除$_，那之前的代码是否不兼容阿。

作者: zhlong8 时间: 2014-04-03 14:24
不建议的是 my $_，这是个错误的实践，并不是要废除默认参数的用法。 5.18 文档中

Lexical $_ is now experimental

Since it was introduced in Perl v5.10, it has caused much confusion with no obvious solution:

Various modules (e.g., List::Util) expect callback routines to use the global $_. use List::Util 'first'; my $_; first { $_ == 1 } @list does not work as one would expect.
A my $_ declaration earlier in the same file can cause confusing closure warnings.
The "_" subroutine prototype character allows called subroutines to access your lexical $_, so it is not really private after all.
Nevertheless, subroutines with a "(@)" prototype and methods cannot access the caller's lexical $_, unless they are written in XS.
But even XS routines cannot access a lexical $_ declared, not in the calling subroutine, but in an outer scope, iff that subroutine happened not to mention $_ or use any operators that default to $_.

It is our hope that lexical $_ can be rehabilitated, but this may cause changes in its behavior. Please use it with caution until it becomes stable.

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