What is the opposite function for (abs) ?

[Michaels]

Hello ,

 

With the function abs we would get the absolute or the possitive number .

Like ..

 

(abs -100)

 

I want to convert a number to be completely negative for example from 100 to be -100 .

 

Is it possible ?

 

Many thanks

[Lee Mac]

  (- 100)  

 

Or rather:

 

(- (abs x))

Edited October 23, 2010 by Lee Mac

[JohnM]

you will have to make your own function to convert a number to a negitive

 

 
;;;- pass the function a positive number
(defun negnum (aug1 / retval )
 (if (not (minusp aug1));_verify its not negitive
(setq retval(- aug1(* aug1 2)));_make it negitive
       );_if
);_defun

[Michaels]

  (- 100)  

 

What a question .

 

I concentrated my thoughts on a function , which prevented me to think of it that way .

 

Thank you Lee.

[Michaels]

you will have to make your own function to convert a number to a negitive

 

 
;;;- pass the function a positive number
(defun negnum (aug1 / retval )
 (if (not (minusp aug1));_verify its not negitive
(setq retval(- aug1(* aug1 2)));_make it negitive
       );_if
);_defun

 

Really nice, Thank you so much JohnM.

 

Appreciated.

[w0nd]

(* -1.0 (abs Variable_Name))

[David Bethel]

or:

(min n (- n))

[Lee Mac]

Another

 

(1+ (~ (abs x)))

[Michaels]

Another

 

(1+ (~ (abs x)))

 

Thanks Lee , Also your code without the 1+ would give a correct result .

 

like....

 (~ (abs 100))

 

So it returns -100 But how to add one and it would not be added to the result ? I do wonder !!!!

 

Appreciated

[Lee Mac]

For positive 'n'

(~ n)

will return -(n+1) (One's complement)

 

The "~" is a bitwise NOT, hence flipping all the bits (including the highest bit which determines the sign of the number [for a signed integer] ).

 

So, say we take an 8-bit signed integer as an example, the 8th bit being the sign bit:

 

           +/- 64 32 16  8  4  2  1
------------------------------------
  n  =       0  1  0  0  1  1  0  1  =    77
(~ n) =       1  0  1  1  0  0  1  0  =  - 78

 

Perhaps see here also: http://en.wikipedia.org/wiki/Signed_number_representations

 

This also has a great explanation:

 

https://developer.mozilla.org/en/JavaScript/Reference/Operators/Bitwise_Operators

[JohnM]

this thread is getting way too negitive for me

[Michaels]

this thread is getting way too negitive for me

 

Why it's being negative fo you ?

 

I am sorry for that .

[Lee Mac]

Also your code without the 1+ would give a correct result .

 

It shouldn't do, as explained in my last post...