Go4Expert - To find a>b or a<b without using of Logical & relational Operators!!!

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- - To find a>b or a<b without using of Logical & relational Operators!!! (http://www.go4expert.com/showthread.php?t=8223)

To find a>b or a<b without using of Logical & relational Operators!!!

Program to find max(x,y) or Min(x,y) without using any relational and logical operator.

Code: C

int maximum(int x, int y)
 {   
   int fNum[2],temp,num[2]; 
   num[0] = x;  
   num[1] = y;    
   temp=fNum[ Fun4Sign(x - y)];   
   return( temp); 
}

int Fun4Sign(int sgn) 
{   
     int temp;   
     temp= unsigned(sgn) >>  (sizeof(int)*8-1);    return(temp); 
}

EXTRA DOSE: One More thing to find min and max...

Code: C

int  MinimumOf( int a, int b)  
{
    return(   b + ((a - b) & ((a - b) >> (sizeof(int) * CHAR_BIT - 1)))  );
}

Code: C

int  MaximumOf( int a, int b)  
{
    return(   a - ((a - b) & ((a - b) >> (sizeof(int) * CHAR_BIT - 1)))  );
}

Re: To find a>b or a<b without using of Logical & relational Operators!!!

Looks like there is some problem in your code where you have not defined num

Re: To find a>b or a<b without using of Logical & relational Operators!!!

That's pretty neat, the perhaps not universally portable.
Your code does better than just avoiding relational and logical operators,
it also avoids conditional (and loop) statements (including ?: ).
Here's a re-write:

Code:

#include <limits.h> /* for CHAR_BIT: number of bits in a char */



#define INT_BITS (sizeof(int) * CHAR_BIT)



int maximum( int x, int y ) {

    int xy[] = { x, y };

    return xy[ getSign( x - y )]; /* Index xy by sign of (x-y) */

}



int getSign( int n ) { /* Returns sign bit of n */

    /* Shift sign into bit position 0 */

    return (unsigned)n >> INT_BITS - 1;

}

One could replace int xy[] = { x, y } by int* xy = &x, but
that assumes (minimally) that x has a lower address than y.
The method is already making an assumption about manipulating
the sign bit that may not work on all computers.

I also found your MinimumOf and MaximumOf interesting:

Code:

    /* Fill n with its sign bit, becoming all 1's or 0's */

#define spread_sign(n) ((n) >> (INT_BITS - 1))



    /* Return zero if n is positive, otherwise return n */

#define zero_if_positive(n) ((n) & spread_sign(n))



int minimumOf( int a, int b ) {

    return b + zero_if_positive( a - b );

}



int maximumOf( int a, int b ) {

    return a - zero_if_positive( a - b );

}

Re: To find a>b or a<b without using of Logical & relational Operators!!!

Quote:

Originally Posted by shabbir

Looks like there is some problem in your code where you have not defined num

Very Very Sorry for this mistake.

correct code will be

Code: C

Code:

int maximum(int x, int y)

 {   

   int fNum[2],temp,num[2]; 

   num[0] = x;  

   num[1] = y;    

  temp=fNum[ Fun4Sign(x - y)];   

  return( temp); 

}



 int Fun4Sign(int sgn) 

{   

     int temp;   

     temp= unsigned(sgn) >>  (sizeof(int)*8-1);    return(temp); 

}

Re: To find a>b or a<b without using of Logical & relational Operators!!!

I have updated the above article but learn to use the code block in the posts - Before you make a query