🚀 go-pugleaf

In article <MATT.95Aug21165410@physics2.Berkeley.EDU>, Warner Losh <imp@village.org> writes:
>: I'm wondering why there isn't a logical XOR operator (eg. ^^)
>: though there is a bitwise one (ie. ^).
>
>The '!=' operator is logically the same as XOR.  It produces the same
>truth table for bool values as you'd expect an xor operator to:

[deletia]

>There can be no short circuit done for this operator, since you can't
>know the result of the operator until you've evaluated both sides.
>Maybe that is why it isn't in the language.  I was once told that C
>had both | and || because one was optimized and the other wasn't.
>Since it is impossible to optimize xor, there is no ^^ operator.  I'm
>not sure how true this actually is.

The optimization stuff is nonsense. The difference is that | is bit-
wise, and || is a logical operator that knows only two values: zero
and non-zero. Hence,
   (1 | 2) == 0, i.e. false if interpreted as boolean, but
   (1 || 2) == 1, i.e. true.

The != operator can only be used as xor if you are certain that
logical values are never represented by any other integers than
0 and 1.


Jesper Larsson                                 ,,,    jesper@dna.lu.se
Dept. of Computer Science, Lund University    (o o)    +46 46 22 24908
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``Bad programming practice can lead to death.''         (P.J. Plauger)
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