"

 COPYRIGHT (c) 1994 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.

"

"{ Package: 'stx:libbasic' }"

Number subclass:#LimitedPrecisionReal

	instanceVariableNames:''

	classVariableNames:''

	poolDictionaries:''

	category:'Magnitude-Numbers'

!

!LimitedPrecisionReal class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1994 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

"

    Abstract superclass for single and double (and maybe more) 

    precision real numbers (i.e. Float and Double).

    Due to historic reasons, ST/X's Floats are what Doubles are in ST-80.

    This may change soon (implementing LPReal is a first step towards this).

    [author:]

        Claus Gittinger

    [see also:]

        Fraction FixedPoint

"

! !

!LimitedPrecisionReal class methodsFor:'instance creation'!

new:aNumber

    "catch this message - not allowed for floats/doubles"

    self error:'Floats/Doubles cannot be created with new:'

! !

!LimitedPrecisionReal methodsFor:'accessing'!

at:index

    "redefined to prevent access to individual bytes in a real."

    self error:'not allowed for floats/doubles'

!

at:index put:aValue

    "redefined to prevent access to individual bytes in a real"

    self error:'not allowed for floats/doubles'

! !

!LimitedPrecisionReal methodsFor:'arithmetic'!

* aNumber

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

"/ as soon as Float are float & Double are doubles,

"/ use:

"/    ^ aNumber productFromDouble:self asDouble

    ^ aNumber productFromFloat:self asFloat

    "Modified: 17.4.1996 / 12:35:36 / cg"

!

+ aNumber

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

"/ as soon as Float are float & Double are doubles,

"/ use:

"/    ^ aNumber sumFromDouble:self asDouble

    ^ aNumber sumFromFloat:self asFloat

    "Modified: 17.4.1996 / 12:35:55 / cg"

!

- aNumber

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

"/ as soon as Float are float & Double are doubles,

"/ use:

"/    ^ aNumber differenceFromDouble:self asDouble

    ^ aNumber differenceFromFloat:self asFloat

    "Modified: 17.4.1996 / 12:36:07 / cg"

!

/ aNumber

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

    ((aNumber == 0) or:[aNumber = 0.0]) ifTrue:[

        ^ DivisionByZeroSignal raiseRequest.

    ].

"/ as soon as Float are float & Double are doubles,

"/ use:

"/    ^ aNumber quotientFromDouble:self asDouble

    ^ aNumber quotientFromFloat:self asFloat

    "Modified: / 17.4.1996 / 12:36:21 / cg"

    "Modified: / 26.7.1999 / 10:46:11 / stefan"

!

// aNumber

    "return the integer quotient of dividing the receiver by aNumber with

     truncation towards negative infinity."

    ^ (self / aNumber) floor asInteger

    "Modified: 5.11.1996 / 11:45:37 / cg"

! !

!LimitedPrecisionReal methodsFor:'coercing & converting'!

asFixedPoint

    "return the receiver as fixedPoint number.

     Q: what should the scale be here ?"

    ^ self asFraction asFixedPoint

    "

     0.3 asFixedPoint

     0.5 asFixedPoint

     (1/5) asFloat asFixedPoint 

     (1/3) asFloat asFixedPoint 

     (2/3) asFloat asFixedPoint 

     (1/8) asFloat asFixedPoint

     3.14159 asFixedPoint

     0.0000001 asFraction

     0.0000001 asFixedPoint

    "

    "Modified: / 25.10.1997 / 15:36:54 / cg"

!

asFixedPoint:scale

    "return the receiver as fixedPoint number with the given

     number of post-decimal-digits."

    ^ self asFraction asFixedPoint:scale

    "

     0.3 asFixedPoint:4     

     0.3 asFixedPoint:3     

     0.3 asFixedPoint:2     

     0.3 asFixedPoint:1     

     0.3 asFixedPoint:0

     0.5 asFixedPoint:3     

     (1/5) asFloat asFixedPoint:1  

     (1/8) asFloat asFixedPoint:1  

     3.14159 asFixedPoint:2       

     3.14159 asFixedPoint:3       

     (3.14159 asFixedPoint:2) asFixedPoint:5  

    "

    "Modified: / 5.8.1998 / 13:29:51 / cg"

!

asFraction

    "Answer a rational number (Integer or Fraction) representing the receiver.

     This conversion uses the continued fraction method to approximate 

     a floating point number."

    |num1 denom1 num2 denom2 int frac newD temp limit|

    limit := (self class unity * 10) raisedTo:self defaultNumberOfDigits.

    num1 := self truncated. 

    denom1 := 1.            "The first of two alternating denominators"

    num2 := 1.              "The second numerator"

    denom2 := 0.            "The second denominator--will update"

    int := num1.            "The integer part of self"

    frac := self fractionPart.             

    [frac = 0] whileFalse:[                

        newD := 1.0 / frac.                   

        int := newD truncated.        

        frac := newD fractionPart.      "save the fractional part for next time"

        temp := num2.                   "old numerator and save it"

        num2 := num1.                         

        num1 := num1 * int + temp.      "Update first numerator"

        temp := denom2.                 "old denominator and save it"

        denom2 := denom1.                    

        denom1 := int * denom1 + temp.  "Update first denominator"

        limit < denom1 ifTrue:[

            "Is ratio past float precision?  If so, pick which of the two ratios to use"

            num2 = 0.0 ifTrue:[

                "Is second denominator 0?"

                ^ Fraction numerator:num1 denominator:denom1

            ].

            ^ Fraction numerator:num2 denominator:denom2

        ]

    ].

    "If fractional part is zero, return the first ratio"

    denom1 = 1 ifTrue:[

        "Am i really an Integer?"

        ^ num1 "Yes, return Integer result"

    ].

    "Otherwise return Fraction result"

    ^ Fraction numerator:num1 denominator:denom1

    "

     1.1 asFraction      

     1.2 asFraction      

     0.3 asFraction   

     0.5 asFraction 

     (1/5) asFloat asFraction

     (1/8) asFloat asFraction  

     (1/13) asFloat asFraction 

     3.14159 asFraction        

     3.14159 asFraction asFloat       

     1.3 asFraction  

     1.0 asFraction  

    "

    "Modified: / 25.10.1997 / 16:41:19 / cg"

!

asInteger

    "return an integer with same value - might truncate"

    |max maxF|

    self isNaN ifTrue:[

        ^ self class

            raise:#domainErrorSignal

            receiver:self

            selector:#asInteger

            errorString:'receiver is NaN in #asInteger'

    ].

    self abs < 2e16 ifTrue:[

        "/ NOTICE: this must be redefined in float

        "/ subclasses to handle the smallinteger range;

        "/ i.e. this may only be invoked for reals

        "/ which are NOT within the smallInt range.

        "/ otherwise, endless recursion is the consequence.

        max := SmallInteger maxVal // 2 + 1.

        maxF := max asFloat.

        ^ (self quo:maxF) * max + (self rem:maxF) truncated

    ].

    ^ self asTrueFraction

    "

     12345.0 asInteger     

     1e15 asInteger        

     1e33 asInteger asFloat

     1e303 asInteger asFloat

    "

    "Modified: 12.2.1997 / 16:45:07 / cg"

!

asRational

    "Answer a Rational number--Integer or Fraction--representing the receiver.

     Same as asFraction fro st-80 compatibility."

    ^ self asFraction

    "

     1.1 asRational      

     1.2 asRational      

     0.3 asRational   

     0.5 asRational 

     (1/5) asFloat asRational

     (1/8) asFloat asRational  

     (1/13) asFloat asRational 

     3.14159 asRational        

     3.14159 asRational asFloat       

     1.3 asRational  

     1.0 asRational  

    "

!

coerce:aNumber

    "return aNumber converted into receivers type"

"/ as soon as Float are float & Double are doubles,

"/ use:

"/    ^ aNumber asDouble

    ^ aNumber asFloat

    "Modified: 17.4.1996 / 12:36:46 / cg"

!

fractionalPart

    "This has been renamed to #fractionPart for ST80 compatibility.

     extract the after-decimal fraction part.

     the floats value is 

        float truncated + float fractionalPart"

    <resource:#obsolete>

    self obsoleteMethodWarning:'please use #fractionPart'.

    ^ self fractionPart

    "Modified: / 28.10.1998 / 17:10:12 / cg"

    "Created: / 28.10.1998 / 17:10:32 / cg"

!

generality

    "return the generality value - see ArithmeticValue>>retry:coercing:"

    ^ 80

! !

!LimitedPrecisionReal methodsFor:'comparing'!

< aNumber

    "return true, if the argument is greater"

"/ as soon as Float are float & Double are doubles,

"/ use:

"/    ^ aNumber lessFromDouble:self asDouble

    ^ aNumber lessFromFloat:self asFloat

    "Modified: 17.4.1996 / 13:34:50 / cg"

!

<= aNumber

    "return true, if the argument is greater or equal"

    ^ self retry:#<= coercing:aNumber

!

= aNumber

    "return true, if the arguments value are equal"

    ^ self retry:#= coercing:aNumber

!

> aNumber

    "return true, if the argument is less"

    ^ self retry:#> coercing:aNumber

!

>= aNumber

    "return true, if the argument is less or equal"

    ^ self retry:#>= coercing:aNumber

!

~= aNumber

    "return true, if the arguments value are not equal"

    ^ self retry:#~= coercing:aNumber

! !

!LimitedPrecisionReal methodsFor:'copying'!

deepCopy

    "return a deep copy of myself

     - because storing into floats is not recommended/allowed, its ok to return the receiver"

    ^ self

!

deepCopyUsing:aDictionary

    "return a deep copy of myself

     - because storing into floats is not recommended/allowed, its ok to return the receiver"

    ^ self

!

shallowCopy

    "return a shallow copy of the receiver"

    ^ self

!

simpleDeepCopy

    "return a deep copy of the receiver

     - because storing into floats is not recommended/allowed, its ok to return the receiver"

    ^ self

! !

!LimitedPrecisionReal methodsFor:'double dispatching'!

differenceFromFraction:aFraction

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

    |d|

    d := aFraction denominator.

    ^ (aFraction numerator - (self * d)) / d

!

productFromFraction:aFraction

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

    ^ self * aFraction numerator / aFraction denominator

!

quotientFromFraction:aFraction

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

    ^ aFraction numerator / (self * aFraction denominator)

!

sumFromFraction:aFraction

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

    |d|

    d := aFraction denominator.

    ^ (self * d + aFraction numerator) / d

! !

!LimitedPrecisionReal methodsFor:'encoding'!

encodeOn:anEncoder with:aParameter

    anEncoder encodeFloat:self with:aParameter

! !

!LimitedPrecisionReal methodsFor:'printing & storing'!

printOn:aStream

    "append a printed representation of the receiver to

     the argument, aStream.

     LimitedPrecisonReal and its subclasses use #printString instead of

     #printOn: as basic print mechanism."

    aStream nextPutAll:self printString

    "Modified: / 20.1.1998 / 14:10:46 / stefan"

!

printString

    "return a printed representation of the receiver

     LimitedPrecisonReal and its subclasses use #printString instead of

     #printOn: as basic print mechanism."

    ^ self subclassResponsibility

    "Created: / 17.4.1996 / 12:12:20 / cg"

    "Modified: / 20.1.1998 / 14:10:47 / stefan"

! !

!LimitedPrecisionReal methodsFor:'queries'!

defaultNumberOfDigits

    self subclassResponsibility

!

size

   "redefined since reals are kludgy (ByteArry)"

   ^ 0

! !

!LimitedPrecisionReal methodsFor:'testing'!

isFinite

   ^ self subclassResponsibility

    "Created: / 7.1.1998 / 12:02:06 / stefan"