[Tutor] xor

[Paul Sidorsky]

Danny Yoo wrote:

> On a tangent note, there's a cute trick that assembly and C programmers
> could use with XOR to swap two values around without using a temporary
> variable.  Here's an interpreter session that shows how it works:

> >>> a = a ^ b
> >>> b = a ^ b
> >>> a = a ^ b

In C this is usually condensed to the ugly but very efficient
a^=b^=a^=b, which I first saw in Abrash's Zen of Graphics Programming. 
Aside from saving space, it's significantly faster.

Of course, this won't work in Python because a ^= b is an assignment and
assignments don't have values in Python.

-- 
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Paul Sidorsky                                          Calgary, Canada
paulsid@shaw.ca                        http://members.shaw.ca/paulsid/