Sort function

[rohitbasu77]

I am little confused what it print for $a and $b, how the comparision is really happening. can you explain.....

#!/usr/bin/perl
 
@array = qw(7 8 59 58 4 5 6 2 59);
 
@array2 = sort {$a <=> $b; print "$a and $b.... comp.. \n"; } @array;
 
 
print "$_\n" for @array2;
 

[numberwhun]

I am little confused what it print for $a and $b, how the comparision is really happening. can you explain.....

#!/usr/bin/perl
 
@array = qw(7 8 59 58 4 5 6 2 59);
 
@array2 = sort {$a <=> $b; print "$a and $b.... comp.. \n"; } @array;
 
 
print "$_\n" for @array2;
 

Here is a link that doesn't do a bad job explaining how sort works. I would read it.


Also, I would read the sort page on perl doc, because you cannot have that print function in the sort. Only the comparison pieces can be in there.

Regards,

Jeff

[rohitbasu77]

Here is a link that doesn't do a bad job explaining how sort works. I would read it.


Also, I would read the sort page on perl doc, because you cannot have that print function in the sort. Only the comparison pieces can be in there.

Regards,

Jeff

thanks , i need only the page from where you find it.

[KevinADC]

The sort function documentation explains what goes on during the sort, here is what the sort functions sees internally:

@array = qw(7 8 8 59 58 4 5 6 2 59);
for my $i (0..$#array) {
    print "$array[$i] <=> $array[$i+1] = ", $array[$i] <=> $array[$i+1],"\n";
}

output:

7 <=> 8 = -1
8 <=> 8 = 0
8 <=> 59 = -1
59 <=> 58 = 1
58 <=> 4 = 1
4 <=> 5 = -1
5 <=> 6 = -1
6 <=> 2 = 1
2 <=> 59 = -1
59 <=>  = 1

-1 means the left operand is less than the right
0 means they are equal
1 means the left operand is greater than the right

the "cmp" and "<=>" operators both work like this. But "cmp" sorts in ASCII order instead of numeric order.

And thats how perl sorts them internally but the comparison is done as many times as needed untill all the data is correctly sorted.

[rohitbasu77]

The sort function documentation explains what goes on during the sort, here is what the sort functions sees internally:

@array = qw(7 8 8 59 58 4 5 6 2 59);
for my $i (0..$#array) {
    print "$array[$i] <=> $array[$i+1] = ", $array[$i] <=> $array[$i+1],"\n";
}

output:

7 <=> 8 = -1
8 <=> 8 = 0
8 <=> 59 = -1
59 <=> 58 = 1
58 <=> 4 = 1
4 <=> 5 = -1
5 <=> 6 = -1
6 <=> 2 = 1
2 <=> 59 = -1
59 <=>  = 1

-1 means the left operand is less than the right
0 means they are equal
1 means the left operand is greater than the right

the "cmp" and "<=>" operators both work like this. But "cmp" sorts in ASCII order instead of numeric order.

And thats how perl sorts them internally but the comparison is done as many times as needed untill all the data is correctly sorted.

Thanks, Yes this is the algorithim which repet in sort function a number of ime unless and untill the whole array is in a sorted manner.