getting unique identifier out of two variables

[JArgyle]

Hi,

given a set of pairs

P = {(x1,y1), (x2,y2), ... (xn,yn)}

where each pair is unique, is there a way to get

Q = {z1, z2, ..., zn}

that is to map each pair of values to another unique one? Is hashing the
only way to achieve this?

Regards

Josè

[JArgyle]

Re: getting unique identifier out of two variables

Stefan Ram wrote:

»That is« is used to join two wordings with the same meaning.
This is not the case here. Moreover, your question only
mentions mathematical concepts, but shows no relation to C++.
>
Yes, for every set P of pairs, there exists a set Q, so that
there exists a mapping f: P -Q, so that f is injective and
f(x) != x. Proof: Map each x to the set {x}.
>

You must have had a very difficult childhood.

Kind Regards

[JArgyle]

Re: getting unique identifier out of two variables

Alf P. Steinbach wrote:

>
Or for example, if they're unsigned char and sizeof(unsigned int)>=2,
then let z = (unsigned(x)<<C HAR_BIT) | unsigned(y).
>

Hi Alf, thanks. In my case they are two unsigned int (I'm evaluating if
two size_t are better though). I was indeed considering to gather them
into a struct and overloading the < operator (as you also suggest), but
I was interested in a more low-level approach, such as the one you
describe over here. Could you expand a bit on this? Supposing I have two
uint32_t would it still possible to do something like this?

Regards

J.