Class: Infinity

• Inheritance
• Description
• Class protocol
  • class initialization
  • errors
  • instance creation
  • queries
• Instance protocol
  • arithmetic
  • coercing & converting
  • comparing
  • double dispatching
  • errors
  • testing
• Private classes
• Examples

Inheritance:

   Object
   |
   +--Magnitude
      |
      +--ArithmeticValue
         |
         +--Number
            |
            +--MetaNumber
               |
               +--Infinity
                  |
                  +--Infinity::NegativeInfinity
                  |
                  +--Infinity::PositiveInfinity

Package:

stx:libbasic

Category:

Magnitude-Numbers

Version:

rev: 1.33 date: 2023/09/16 09:16:51

user: cg

file: Infinity.st directory: libbasic

module: stx stc-classLibrary: libbasic

Description:

I have two instances representing positive and negative infinity.
These are singletons used by non-floats (which have individual Inf representations).

Claus: fixed some minor bugs (args to errorUndefinedResult:) and some wrong comments.
       Changed retry:coercing: to match ST/X's way of doing this

Instance Variables :-

copyright
This is a Manchester Goodie.  It is distributed freely on condition
that you observe these conditions in respect of the whole Goodie, and on
any significant part of it which is separately transmitted or stored:
       * You must ensure that every copy includes this notice, and that
         source and author(s) of the material are acknowledged.
       * These conditions must be imposed on anyone who receives a copy.
       * The material shall not be used for commercial gain without the prior
         written consent of the author(s).

For more information about the Manchester Goodies Library (from which 
this file was distributed) send e-mail:
       To: goodies-lib@cs.man.ac.uk
       Subject: help 

This is an additional goody-class, which is NOT covered by the
ST/X license. It has been packaged with the ST/X distribution to
make your live easier instead. NO WARRANTY.

info
    NAME            infinity
    AUTHOR          manchester
    FUNCTION        Provides a class of infinities
    ST-VERSION      2.2
    PREREQUISITES   
    CONFLICTS
    DISTRIBUTION    world
    VERSION         1
    DATE            22 Jan 1989
    SUMMARY
 This is a set of changes that implements infinity in the Number hierarchy.  
 I obtained the original changes from the author of an article in comp.lang.smalltalk.
 I have just installed it in my image and I have found two small omissions
 which are corrected in what is below; there might be others.  Arithmetic
 between infinities is not defined but magnitude comparisons are implemented.

Class protocol:

 initialize

initialize my two singleton instances

Usage example(s):

Infinity initialize

 errorUndefinedResult: messageSelector from: aReceiver

 negative

Return the unique instance of negative infinity

Usage example(s):

Infinity negative negated Infinity negative abs Infinity positive = Float infinity Infinity negative = Float negativeInfinity Infinity negative = Float infinity

 negative: aBoolean

Return either instance of negative infinity

 new

only my two singleton instances are allowed;
get either via Infinity positive or Infinity negative

 positive

Return the unique instance of positive infinity

 isAbstract

Return if this class is an abstract class.
True is returned here for myself only; false for subclasses.
Abstract subclasses must redefine this again.

Instance protocol:

 * aNumber

Multiply the receiver by the argument and answer with the result.

 + aNumber

Add the receiver and the argument and answer with the result.

 - aNumber

Subtract aNumber from the receiver and answer the result.

 / aNumber

Divide the receiver by the argument and answer the result.

 generality

Infinities are more general than scalars, but not more general than
vectors (e.g. Points)

 < aNumber

Positive infinity is greater than any number other than positive infinity.
Analogously, negative infinity is less than any other number other
than negative infinity

Usage example(s):

Infinity positive < 0 Infinity positive < 1000 Infinity positive < -1000 Infinity positive < Infinity positive Infinity positive < Infinity negative 0 < Infinity positive 1000 < Infinity positive -1000 < Infinity positive Infinity negative < Infinity positive Infinity negative < 0 Infinity negative < 1000 Infinity negative < -1000 Infinity negative < Infinity negative Infinity negative < Infinity positive 0 < Infinity negative 1000 < Infinity negative -1000 < Infinity negative Infinity negative < Infinity positive

 = aNumber

return true, if the argument represents the same numeric value
as the receiver, false otherwise.

 > aNumber

Positive infinity is greater than any number other than positive infinity.
Analogously, negative infinity is less than any other number other
than negative infinity

Usage example(s):

Infinity positive > 0 Infinity positive > 1000 Infinity positive > -1000 Infinity positive > Infinity positive Infinity positive > Infinity negative 0 > Infinity positive 1000 > Infinity positive -1000 > Infinity positive Infinity negative > Infinity positive Infinity negative > 0 Infinity negative > 1000 Infinity negative > -1000 Infinity negative > Infinity negative Infinity negative > Infinity positive 0 > Infinity negative 1000 > Infinity negative -1000 > Infinity negative Infinity negative > Infinity positive

 differenceFromSomeNumber: aNumber

Sent from aNumber-self, if aNumber does not know how to handle this

 equalFromSomeNumber: aNumber

Sent from aNumber = self, if aNumber does not know how to handle this.
Return true if aNumber = self.

 lessFromSomeNumber: aNumber

Sent from aNumber < self, if aNumber does not know how to handle this.
Return true if aNumber < self.

 productFromSomeNumber: aNumber

Sent from aNumber*self, if aNumber does not know how to handle this

 quotientFromSomeNumber: aNumber

Return the quotient of the argument, aNumber and the receiver.
Sent when aNumber does not know how to divide by the receiver.

 sumFromSomeNumber: aNumber

Sent from aNumber+self, if aNumber does not know how to handle this

 errorUndefinedResult: messageSelector

 isFinite

return true, if the receiver is a finite float (not NaN and not +/-INF)

 isInfinite

return true, if the receiver is an infinite number (+Inf or -Inf)

Private classes:

    NegativeInfinity
    PositiveInfinity

Examples:

1 + Infinity positive   
Infinity positive + 1     
Infinity positive + Infinity positive     

Infinity negative - 1                   
Infinity negative + Infinity negative   
Infinity negative + Infinity negative   

Infinity negative negated              
Infinity positive negated              

Infinity positive > Infinity negative  
Infinity negative > Infinity positive  

Infinity negative + Infinity positive   -> raises an error
Infinity negative - Infinity negative   -> raises an error