Why can't I xor strings?

[Andrew Dalke]

Alex
>     str1 != str2 and (str1+str2) == (str2+str1)
> 
> I guess I'd better stop here because I can't actually _prove_ the last
> one of these actually implies one of the strings is empty but I can't
> find counterexamples either...!-)

str1 = "a"
str2 = "aa"

				Andrew
				dalke at dalkescientific.com