在 Perl 中访问哈希数组

Question

1. I have problem with accessing a hash in each element of array after creating it but it gave the last element. What should I do to access all the elements of my array?
2. When I want push a hash to an array I use {} instead of () because if I don't it gave me error. How does it see when I use {}?

    @stem = ();
    for ($i = 0; $i < 2; ++$i) {
        push @stem, { u1 => 1, u2 => 2 , u3 => 3 };
    }

    @ants = ();
    $count = 0;
    for ($i = 0; $i < scalar(@stem); ++$i) {
        @allowed = ();
        %hash = ();
        for ($j = 0; $j < scalar(@stem); ++$j) {
            push @allowed, { stem => ++$count, hinfo => ++$count };
        }
        %hash = (allowed => \@allowed, solution => ++$count);
        push (@ants, \%hash);
    }

    for ($i = 0; $i < scalar(@ants); ++$i) {

        %test = %{$ants[$i]};
        print "=>", $test{solution}, "\n";
        @temp = @{$test{allowed}};

        for ($j = 0; $j < scalar(@temp); ++$j) {
            print $j, ":", $temp[$j]->{stem}, " ", $temp[$j]->{hinfo}, "\n";
        }
    }

Output:

=>21
0:16 16
1:18 18
2:20 20
=>21
0:16 16
1:18 18
2:20 20

Answer 1

2) When I want push a hash to an array I use {} instead of () because if I don't it gave me error. How does it see when I use {} ?

I can answer this Question 2.

When you use () perl sees as list of elements. When you use {} perl sees it as reference to a hash.

So When you do this: push @Arr, (x=>2, y=>5); four elements will be pushed to @Arr : x , 2 , y , 5 . Which is not your intention.

But When you do this: push @Arr , {x => 2, y => 5}; a single reference to an anonymous hash containing x and y as the keys, and 2 and 5 as the respective values will be pushed to @Arr .