windows-nt/Source/XPSP1/NT/shell/osshell/accesory/ratpak/rat.c

//-----------------------------------------------------------------------------
//  Package Title  ratpak
//  File           rat.c
//  Author         Timothy David Corrie Jr. (timc@microsoft.com)
//  Copyright      (C) 1995-96 Microsoft
//  Date           01-16-95
//
//
//  Description
//
//  Contains mul, div, add, and other support functions for rationals.
//
//
//
//-----------------------------------------------------------------------------

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <stdlib.h>
#if defined( DOS )
#include <dosstub.h>
#else
#include <windows.h>
#endif
#include <ratpak.h>


//-----------------------------------------------------------------------------
//
//    FUNCTION: gcdrat
//
//    ARGUMENTS: pointer to a rational.
//
//
//    RETURN: None, changes first pointer.
//
//    DESCRIPTION: Divides p and q in rational by the G.C.D.
//    of both.  It was hoped this would speed up some
//    calculations, and until the above trimming was done it
//    did, but after trimming gcdratting, only slows things
//    down.
//
//-----------------------------------------------------------------------------

void gcdrat( PRAT *pa )

{
    PNUMBER pgcd=NULL;
    PRAT a=NULL;

    a=*pa;
    pgcd = gcd( a->pp, a->pq );

    if ( !zernum( pgcd ) )
        {
        divnumx( &(a->pp), pgcd );
        divnumx( &(a->pq), pgcd );
        }

    destroynum( pgcd );
    *pa=a;
    
}

//-----------------------------------------------------------------------------
//
//    FUNCTION: fracrat
//
//    ARGUMENTS: pointer to a rational a second rational.
//
//    RETURN: None, changes pointer.
//
//    DESCRIPTION: Does the rational equivalent of frac(*pa);
//
//-----------------------------------------------------------------------------

void fracrat( PRAT *pa )

{
    long trim;
    remnum( &((*pa)->pp), (*pa)->pq, BASEX );
    
    //Get *pa back in the integer over integer form.
    RENORMALIZE(*pa);
}


//-----------------------------------------------------------------------------
//
//    FUNCTION: mulrat
//
//    ARGUMENTS: pointer to a rational a second rational.
//
//    RETURN: None, changes first pointer.
//
//    DESCRIPTION: Does the rational equivalent of *pa *= b.
//    Assumes nRadix is the nRadix of both numbers.
//
//-----------------------------------------------------------------------------

void mulrat( PRAT *pa, PRAT b )
    
    {
    // Only do the multiply if it isn't zero.
    if ( !zernum( (*pa)->pp ) )
        {
        mulnumx( &((*pa)->pp), b->pp );
        mulnumx( &((*pa)->pq), b->pq );
        trimit(pa);
        }
    else
        {
        // If it is zero, blast a one in the denominator.
        DUPNUM( ((*pa)->pq), num_one );
        }

#ifdef MULGCD
    gcdrat( pa );
#endif

}

//-----------------------------------------------------------------------------
//
//    FUNCTION: divrat
//
//    ARGUMENTS: pointer to a rational a second rational.
//
//    RETURN: None, changes first pointer.
//
//    DESCRIPTION: Does the rational equivalent of *pa /= b.
//    Assumes nRadix is the nRadix of both numbers.
//
//-----------------------------------------------------------------------------


void divrat( PRAT *pa, PRAT b )

{

    if ( !zernum( (*pa)->pp ) )
        {
        // Only do the divide if the top isn't zero.
        mulnumx( &((*pa)->pp), b->pq );
        mulnumx( &((*pa)->pq), b->pp );

        if ( zernum( (*pa)->pq ) )
            {
            // raise an exception if the bottom is 0.
            throw( CALC_E_DIVIDEBYZERO );
            }
        trimit(pa);
        }
    else
        {
        // Top is zero.
        if ( zerrat( b ) )
            {
            // If bottom is zero
            // 0 / 0 is indefinite, raise an exception.
            throw( CALC_E_INDEFINITE );
            }
        else
            {
            // 0/x make a unique 0.
            DUPNUM( ((*pa)->pq), num_one );
            }
        }

#ifdef DIVGCD
    gcdrat( pa );
#endif 

}

//-----------------------------------------------------------------------------
//
//    FUNCTION: subrat
//
//    ARGUMENTS: pointer to a rational a second rational.
//
//    RETURN: None, changes first pointer.
//
//    DESCRIPTION: Does the rational equivalent of *pa += b.
//    Assumes base is internal througought.
//
//-----------------------------------------------------------------------------

void subrat( PRAT *pa, PRAT b )

{
    b->pp->sign *= -1;
    addrat( pa, b );
    b->pp->sign *= -1;
}

//-----------------------------------------------------------------------------
//
//    FUNCTION: addrat
//
//    ARGUMENTS: pointer to a rational a second rational.
//
//    RETURN: None, changes first pointer.
//
//    DESCRIPTION: Does the rational equivalent of *pa += b.
//    Assumes base is internal througought.
//
//-----------------------------------------------------------------------------

void addrat( PRAT *pa, PRAT b )

{
    PNUMBER bot=NULL;

    if ( equnum( (*pa)->pq, b->pq ) )
        {
        // Very special case, q's match., 
        // make sure signs are involved in the calculation
        // we have to do this since the optimization here is only 
        // working with the top half of the rationals.
        (*pa)->pp->sign *= (*pa)->pq->sign; 
        (*pa)->pq->sign = 1;
        b->pp->sign *= b->pq->sign; 
        b->pq->sign = 1;
        addnum( &((*pa)->pp), b->pp, BASEX );
        }
    else
        {
        // Usual case q's aren't the same.
        DUPNUM( bot, (*pa)->pq );
        mulnumx( &bot, b->pq );
        mulnumx( &((*pa)->pp), b->pq );
        mulnumx( &((*pa)->pq), b->pp );
        addnum( &((*pa)->pp), (*pa)->pq, BASEX );
        destroynum( (*pa)->pq );
        (*pa)->pq = bot;
        trimit(pa);
        
        // Get rid of negative zeroes here.
        (*pa)->pp->sign *= (*pa)->pq->sign; 
        (*pa)->pq->sign = 1;
        }

#ifdef ADDGCD
    gcdrat( pa );
#endif 

}



//-----------------------------------------------------------------------------
//
//  FUNCTION: rootrat
//
//  PARAMETERS: y prat representation of number to take the root of
//              n prat representation of the root to take.
//
//  RETURN: bth root of a in rat form.
//
//  EXPLANATION: This is now a stub function to powrat().
//
//-----------------------------------------------------------------------------

void rootrat( PRAT *py, PRAT n )

{
    PRAT oneovern=NULL;

    DUPRAT(oneovern,rat_one);
    divrat(&oneovern,n);

    powrat( py, oneovern );

    destroyrat(oneovern);
}


//-----------------------------------------------------------------------------
//
//    FUNCTION: zerrat
//
//    ARGUMENTS: Rational number.
//
//    RETURN: Boolean
//
//    DESCRIPTION: Returns true if input is zero.
//    False otherwise.
//
//-----------------------------------------------------------------------------

BOOL zerrat( PRAT a )

{
    return( zernum(a->pp) );
}