Integer encoding challenge

ruby-talk
1

Hey all,

I need to come up with a way to encode an integer as a string so that
it will sort correctly lexicographically. This is pretty easy when you
have a fixed integer range but how do you do it with Ruby's BigNums?
Any ideas?

Cheers,
Dave

2

"David Balmain" <dbalmain.ml@gmail.com> writes:

Hey all,

I need to come up with a way to encode an integer as a string so that
it will sort correctly lexicographically. This is pretty easy when you
have a fixed integer range but how do you do it with Ruby's BigNums?
Any ideas?

Cheers,
Dave

def encode_integer(num)
  "x"*num
end

Do I win something?

YS.

3

Nice idea :stuck_out_tongue:
But how about negative numbers.

···

On 7/19/06, Yohanes Santoso <ysantoso-rubytalk@dessyku.is-a-geek.org> wrote:

"David Balmain" <dbalmain.ml@gmail.com> writes:

> Hey all,
>
> I need to come up with a way to encode an integer as a string so that
> it will sort correctly lexicographically. This is pretty easy when you
> have a fixed integer range but how do you do it with Ruby's BigNums?
> Any ideas?
>
> Cheers,
> Dave

def encode_integer(num)
  "x"*num
end

Do I win something?

YS.

4

"David Balmain" <dbalmain.ml@gmail.com> writes:

···

On 7/19/06, Yohanes Santoso <ysantoso-rubytalk@dessyku.is-a-geek.org> wrote:

"David Balmain" <dbalmain.ml@gmail.com> writes:

> Hey all,
>
> I need to come up with a way to encode an integer as a string so that
> it will sort correctly lexicographically. This is pretty easy when you
> have a fixed integer range but how do you do it with Ruby's BigNums?
> Any ideas?
>
> Cheers,
> Dave

def encode_integer(num)
  "x"*num
end

Do I win something?

YS.

Nice idea :stuck_out_tongue:
But how about negative numbers.

Same technique, but put them in different namespace.

YS.

5

I need to be able to compare positive integers with negative so I
would need to add a bit to this technique, (not to mention a couple of
terabytes of memory to handle even moderately large numbers :))

def encode_integer(int)
  if (int > 0)
    "z" * int
  else
    "x" * -int + "y"
  end
end

Anyway, here is a better solution using only only digits 0-9. I'll
extend it myself to use the full ascii alphabet;

def encode_int(int)
  if (int > 0)
    int_str = int.to_s
    ("3%04d" % int_str.size) + int_str
  elsif (int < 0)
    int_str = (-int).to_s
    ("1%04d" % (9999 - int_str.size)) + (10 ** (int_str.size + 1) + int).to_s
  else
    "2"
  end
end

Cheers,
Dave

···

On 7/19/06, Yohanes Santoso <ysantoso-rubytalk@dessyku.is-a-geek.org> wrote:

"David Balmain" <dbalmain.ml@gmail.com> writes:

> On 7/19/06, Yohanes Santoso <ysantoso-rubytalk@dessyku.is-a-geek.org> wrote:
>> "David Balmain" <dbalmain.ml@gmail.com> writes:
>>
>> > Hey all,
>> >
>> > I need to come up with a way to encode an integer as a string so that
>> > it will sort correctly lexicographically. This is pretty easy when you
>> > have a fixed integer range but how do you do it with Ruby's BigNums?
>> > Any ideas?
>> >
>> > Cheers,
>> > Dave
>>
>> def encode_integer(num)
>> "x"*num
>> end
>>
>> Do I win something?
>>
>> YS.
>
> Nice idea :stuck_out_tongue:
> But how about negative numbers.

Same technique, but put them in different namespace.

YS.