"

 COPYRIGHT (c) 1989 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

Number subclass:#Fraction

!

!Fraction class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1989 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

!

documentation

"

    Instances of Fraction represent fractional numbers consisting of

    a numerator and denominator. Both are themselfes arbitrary precision

    integers. Fractions are usually created by dividing Integers using /

    (for exact division)."

! !

!Fraction class methodsFor:'initialization'!

initialize

    FractionZero isNil ifTrue:[

	FractionZero := self numerator:0 denominator:1.

	FractionOne := self numerator:1 denominator:1

    ]

! !

!Fraction class methodsFor:'instance creation'!

new

    "create and return a new fraction with value 0"

    ^ self numerator:0 denominator:1

!

numerator:num denominator:den

    "create and return a new fraction with numerator num and denominator den"

%{  /* NOCONTEXT */

    /* this check allows subclassing .. */

    if (self == Fraction) {

	if (_CanDoQuickAlignedNew(sizeof(struct __fraction))) {

	    OBJ newFraction;

	    int spc;

	    _qCheckedAlignedNew(newFraction, sizeof(struct __fraction));

	    _InstPtr(newFraction)->o_class = Fraction;

	    _FractionInstPtr(newFraction)->f_numerator = num;

	    _FractionInstPtr(newFraction)->f_denominator = den;

	    if (! __bothSmallInteger(num, den)) {

		spc = __qSpace(newFraction);

		__STORE_SPC(newFraction, num, spc);

		__STORE_SPC(newFraction, den, spc);

	    }

	    RETURN ( newFraction );

	}

    }

%}

.

    ^ self basicNew setNumerator:num denominator:den

! !

!Fraction class methodsFor:'queries'!

isBuiltInClass

    "this class is known by the run-time-system"

    ^ self == Fraction

! !

!Fraction methodsFor:'accessing'!

denominator

    "return the denominator"

    ^ denominator

!

! !

!Fraction methodsFor:'arithmetic'!

+ aNumber

    "return the sum of the receiver and the argument, aNumber"

    |n d|

    (aNumber isMemberOf:SmallInteger) ifTrue:[

	^ (self class numerator:(numerator + (denominator * aNumber))

		    denominator:denominator) reduced

    ].

    aNumber isFraction ifTrue:[

	n := aNumber numerator.

	d := aNumber denominator.

	"save a multiplication if possible"

	denominator == d ifTrue:[

	    ^ (self class numerator:(numerator + n) denominator:d) reduced

	].

	^ (self class numerator:((numerator * d) + (n * denominator))

		    denominator:(denominator * d)) reduced

    ].

    (aNumber isMemberOf:Float) ifTrue:[

	^ aNumber + (numerator asFloat / denominator asFloat)

    ].

    ^ aNumber sumFromFraction:self

!

- aNumber

    "return the difference of the receiver and the argument, aNumber"

    |n d|

    (aNumber isMemberOf:SmallInteger) ifTrue:[

	^ (self class numerator:(numerator - (denominator * aNumber))

		    denominator:denominator) reduced

    ].

    aNumber isFraction ifTrue:[

	n := aNumber numerator.

	d := aNumber denominator.

	"save a multiplication if possible"

	denominator == d ifTrue:[

	    ^ (self class numerator:(numerator - n) denominator:d) reduced

	].

	^ (self class numerator:((numerator * d) - (n * denominator)) 

		    denominator:(denominator * d)) reduced

    ].

    (aNumber isMemberOf:Float) ifTrue:[

	^ (numerator asFloat / denominator asFloat) - aNumber

    ].

    ^ aNumber differenceFromFraction:self

!

/ aNumber

    "return the quotient of the receiver and the argument, aNumber"

    |n d|

    (aNumber isMemberOf:SmallInteger) ifTrue:[

	^ (self class numerator:numerator

		    denominator:(denominator * aNumber)) reduced

    ].

    aNumber isFraction ifTrue:[

	n := numerator * aNumber denominator.

	d := denominator * aNumber numerator.

	^ (self class numerator:n denominator:d) reduced

    ].

    (aNumber isMemberOf:Float) ifTrue:[

	^ numerator / (denominator * aNumber)

    ].

    ^ aNumber quotientFromFraction:self

!

// aNumber

    "return the integer quotient of the receiver and the argument, aNumber"

    self negative ifTrue:[

	 ^ ((numerator * aNumber denominator) // (denominator * aNumber numerator)) - 1

    ].

    ^ (numerator * aNumber denominator) // (denominator * aNumber numerator)

!

negated

    "optional - could use inherited method ..."

    ^ self class numerator:(numerator negated)

	       denominator:denominator

!

reciprocal

    "optional - could use inherited method ..."

    numerator == 1 ifTrue:[^ denominator].

    ^ self class numerator:denominator

	       denominator:numerator

! !

    ^ numerator // denominator

!

    ].

! !

!Fraction methodsFor:'double dispatching'!

!

differenceFromInteger:anInteger

    "sent when an integer does not know how to subtract the receiver, a fraction"

    ^ (self class numerator:((anInteger * denominator) - numerator)

		denominator:denominator) reduced

!

productFromInteger:anInteger

    "sent when an integer does not know how to multiply the receiver, a fraction"

    ^ (self class numerator:(anInteger * numerator)

		denominator:denominator) reduced

!

quotientFromInteger:anInteger

    "sent when an integer does not know how to divide by the receiver, a fraction"

    ^ (self class numerator:(anInteger * denominator)

		denominator:numerator) reduced

!

sumFromFloat:aFloat

    "sent when a float does not know how to add the receiver, a fraction"

    ^ (aFloat * denominator + numerator) / denominator

!

! !

!Fraction methodsFor:'printing & storing'!

printOn:aStream

    "append a printed representation of the receiver to the

     argument, aStream"

    aStream nextPut:$(.

    numerator printOn:aStream.

    aStream nextPut:$/.

    denominator printOn:aStream.

    aStream nextPut:$)

! !