Re: Binary math operations (and, or, etc.)
Re: Binary math operations (and, or, etc.)
- Subject: Re: Binary math operations (and, or, etc.)
- From: Chris Page <email@hidden>
- Date: Mon, 13 Jun 2005 12:55:26 -0700
On Jun 8, 2005, at 09:19, Doug McNutt wrote:
In C, the [program]
- 2^2 returns -4
while in AppleScript
- 2^2 returns +4
Without worrying about AppleScript's problems previously discussed,
why does the C function work at all?
Because unary minus has higher precedence than exclusive-or.
First, for those who don't already know, in C, "^" is the exclusive-or
operator, not the "power" operator.
"2^2" on its own produces zero. However, the above calculation is "(-2)
xor 2". Here's a C program that demonstrates. Put this code in a file
named "xortest.c":
#include <stdio.h>
int main ()
{
printf("-2^2 = %d\n", -2^2 );
printf("-(2^2) = %d\n", -(2^2));
printf("(-2)^2 = %d\n", (-2)^2);
printf("-2^3 = %d\n", -2^3);
}
Then compile and run it:
% gcc xortest.c
% ./a.out
-2^2 = -4
-(2^2) = 0
(-2)^2 = -4
-2^3 = -3
The last line shows that it is only a deceptive coincidence that "-2^2
= -4" looks like "-(2 to the power of 2)". If you change either of the
two numbers the result no longer looks confusingly like "^" is the
"power" operator.
--
Chris Page - Software Wrangler - Dylan Pundit
That’s “Chris” with a silent *and* invisible “3”.
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