On 2013-01-22 18:26, Ferrous Cranus wrote:
Τη Τρίτη, 22 Ιανουαρίου 2013 6:11:20 μ.μ. UTC+2, ο χρήστης Chris Angelico
έγραψε:
On Wed, Jan 23, 2013 at 2:59 AM, Ferrous Cranus <nikos.gr...@gmail.com> wrote:
> I just need a way to CONVERT a string(absolute path) to a 4-digit unique
number with INT!!! That's all i want!! But i cannot make it work :(
Either you are deliberately trolling, or you have a major
comprehension problem. Please go back and read, carefully, all the
remarks you've been offered in this thread. Feel free to ask for
clarification of anything that doesn't make sense, but be sure to read
all of it. You are asking something that is fundamentally
impossible[1]. There simply are not enough numbers to go around.
ChrisA
[1] Well, impossible in decimal. If you work in base 4294967296, you
could do what you want in four "digits".
Fundamentally impossible?
Yes.
Well....
OK: How about this in Perl:
$ cat testMD5.pl
use strict;
foreach my $url(qw@ /index.html /about/time.html @){
hashit($url);
}
sub hashit {
my $url=shift;
my @ltrs=split(//,$url);
my $hash = 0;
foreach my $ltr(@ltrs){
$hash = ( $hash + ord($ltr)) %10000;
}
printf "%s: %0.4d\n",$url,$hash
}
which yields:
$ perl testMD5.pl
/index.html: 1066
/about/time.html: 1547
That shortens the int to 4 digits.
A hash isn't guaranteed to be unique. A hash is an attempt to make an
int which is highly sensitive to a change in the data so that a small
change in the data will result in a different int. If the change is big
enough it _could_ give the same int, but the hope is that it probably
won't. (Ideally, if the hash has 4 decimal digits, you'd hope that the
chance of different data giving the same hash would be about 1 in
10000.)
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