Create unique number from 2 numbers is there some way to create unique number from 2 positive integer numbers? Result must be unique even for these pairs: 2 and 30, 1 and 15, 4 and 60. In general, if I take 2 random numbers result must be unique(or with very high probability unique)
Thanks a lot
EDIT: calculation is for computer program,so computational complexity is important
 A: The sort of function you are looking for is often called a pairing function. 
A standard example is the Cantor pairing function $\mathbb{N}\times\mathbb{N}\rightarrow\mathbb{N}$, given by:
$\pi(a,b) = \frac{1}{2}(a+b)(a+b+1) + b$.
You can find more information here: http://en.wikipedia.org/wiki/pairing_function
A: Google pairing function. As I mentioned in the similar question, there are also other pairing functions besides the well-known one due to Cantor. For example, see this "elegant" pairing function, which has the useful property that it orders many expressions by depth.
A: For positive integers as arguments and where argument order doesn't matter:


*

*Here's an unordered pairing function:
$<x, y> = x * y + trunc(\frac{(|x - y| - 1)^2}{4}) = <y, x>$

*For x ≠ y, here's a unique unordered pairing function:
<x, y> = if x < y:
           x * (y - 1) + trunc((y - x - 2)^2 / 4)
         if x > y:
           (x - 1) * y + trunc((x - y - 2)^2 / 4)
       = <y, x>

A: if the numbers are $a$ and $b$, take $2^a3^b$. This method works for any number of numbers (just take different primes as the bases), and all the numbers are distinct.
A: You could try the function by Matthew Szudzik, which is given as:
$$a \geq b ~?~ a*a + a + b : a+b*b$$ 
In other words: $$(a,b)\mapsto \begin{cases} a^2 + a + b & \text{if } a \geq b\\
a + b^2 & \text{if } a < b
\end{cases}$$
I found it here, which is a similar question as this.
A: Apologies for resurrecting this ancient question, but I've noticed that there are collisions in the results of the Cantor pairing function. 
For example, I've noticed that when a and b are 0.0 and 0.0, or 0.6 and 0.0 the result is the same: 0.48.
Is this function expected to work for non-discrete numbers, or does this have something to do with the fact they the numbers are 0.0 and 0.0 in the former case?
