对于字符串比较,perl是否有+/-无穷大的等价项?

空字符串或 undef

没有比其他字符串大的有限字符串。但是,如果可以做出某些假设,比如循环中的所有字符串都是ASCII字符串,那么可以指定一个大于所有字符串的字符串,比如“\x80”(ASCII值128)。

不,但是 ""

(chr(~0)将需要 no warnings 'utf8' ,因为它不在定义的utf8字符范围内。)

package String::Infinity;

use overload
    '""'  => sub {
        return "Infinity"
    },
    'cmp' => sub {
        my($left, $right, $reverse) = @_;
        return 0 if ref $right && $right->isa("String::Infinity");
        return $reverse ? -1 : 1;
    },
    fallback => 1
;

sub new {
    my $class = shift;
    return bless \Inf, $class;
}


use Test::More;

my $inf = String::Infinity->new;
is "$inf", "Infinity",  "stringification";
ok $inf eq $inf,        "equals itself"; 
ok $inf ne "foo",       "  doesn't equal anything else";
ok $inf ne "Infinity",  "  even what it stringifies to";
ok $inf gt "lfkdlk",    "  greater than";
ok !$inf lt "lkafj",    "  not less than";
is $inf cmp "lkjd", 1,  "  cmp";
is "ldfjal;kjd" cmp $inf, -1,   "  cmp reversed";

done_testing;