What is the perl equivalent of MAX_INT?

问题

I am new to perl and seeking the lowest value in an @array. Is there some constant that represents a very large integer number?

I know I could sort the array and take the beginning, but that seems to be a lot of wasted CPU cycles. What is an elegant solution to my problem in Perl?

回答1:

In the general case, you can use undef to signal a non-existent value; perl scalars aren't restricted to holding just integers. That would be written:

my $min; # undef by default
for my $value (@array) {
  $min = $value if !defined $min or $value < $min;
}

But there are some simpler options here. For example, initialize $min to the first value in the array, then compare to the rest:

my $min = $array[0];
for my $i (1 .. $#array) {
  $min = $array[$i] if $array[$i] < $min;
}

Or just use a built-in function:

use List::Util 'min';
my $min = min @array;

回答2:

To answer you the question you actually asked (even though it's not really of use to you):

Largest integer value that can be stored as a signed integer.
```
say ~0 >> 1;
```
Largest integer value that can be stored as an unsigned integer.
```
say ~0;
```
All integer values from 0 to this number can be stored without loss as a floating point number.
```
use Config qw( %Config );
say eval($Config{nv_overflows_integers_at});
```
Note that some larger integers can be stored without loss in a floating point number, but not the one 1 higher than this.

回答3:

9**9**9 works. So does 0+'inf' on many versions/platforms of perl.

回答4:

Perl isn't C; if you try to compute an integer that's too large, you get a floating-point result instead (unless you use bigint, which makes integers unbounded). Beyond that, you get inf.

You can see this with Devel::Peek, which shows you Perl's internal representation of a value:

$ perl -E 'use Devel::Peek; Dump(1000); Dump(1000**100); Dump(1000**100 + 1)'
SV = IV(0xcdf290) at 0xcdf2a0
  REFCNT = 1
  FLAGS = (PADTMP,IOK,READONLY,pIOK)
  IV = 1000
SV = NV(0xd04f20) at 0xcdf258
  REFCNT = 1
  FLAGS = (PADTMP,NOK,READONLY,pNOK)
  NV = 1e+300
SV = NV(0xd04f18) at 0xcdf228
  REFCNT = 1
  FLAGS = (PADTMP,NOK,READONLY,pNOK)
  NV = 1e+300

IV indicates an integer value; NV indicates a floating-point (Number?) value.

You should definitely use a tool suited to your purpose instead of a fuzzy hack; List::Util::min as mentioned in another answer is excellent. Just thought you might like confirmation on your original question :)