Exponential operator

[Michel Fortin]

On 2009-08-07 13:01:55 -0400, Daniel Keep <daniel.keep.lists at gmail.com> said:

> Michel Fortin wrote:
>> I always wondered why there isn't an XOR logical operator.
>> 
>> binary     logical
>> (a & b) => (a && b)
>> (a | b) => (a || b)
>> (a ^ b) => (a ^^ b)
> 
>  a | b | a ^^ b | a != b
> ---+---+--------+--------
>  F | F |   F    |   F
>  F | T |   T    |   T
>  T | F |   T    |   T
>  T | T |   F    |   F
> 
> That's why.

For this table to work, a and b need to be boolean values. With && and 
||, you have an implicit convertion to boolean, not with !=. So if a == 
1 and b == 2, an hypothetical ^^ would yeild false since both are 
converted to true, while != would yield false.

But I have another explanation now. With && and ||, there's always a 
chance that the expression on the left won't be evaluated. If that 
wasn't the case, the only difference in && vs. &, and || vs. | would be 
the automatic convertion to a boolean value. With ^^, you always have 
to evaluate both sides, so it's less useful.

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/