Infinity?

[Andreas Raab]

Hi Andrew,

I think your questions are better asked at the Squeak developers mailing
list - there are plenty of people who will be able to discuss these
issues over there. Please check out
http://lists.squeakfoundation.org/listinfo/squeak-dev for the archives
and more information.

Cheers,
  - Andreas

> -----Original Message-----
> From: owner-squeakland at squeakland.org 
> [mailto:owner-squeakland at squeakland.org] On Behalf Of Andrew Henrick
> Sent: Wednesday, October 09, 2002 10:53 PM
> To: squeakland at squeakland.org
> Subject: Infinity?
> 
> 
> Hello everyone,
> 
> I am a new comer to Squeak and I have a few questions.  My 
> background in 
> Smalltalk  (and the Squeak version of it) is pathetic so 
> please excuse 
> my ignorance.  Also please let me know if I am posting to the wrong 
> list.  The only real reference I have is "Squeak: A Quick Trip to 
> ObjectLand."  In any case, here they are:
> 
> Q1.  Is there some way to have the browser colorize and indent on the 
> fly as I write code?  Right now, I just select "colorPrint" and that 
> formats text that has been accepted by the "system," but is there 
> anything better?
> 
> Q2.  I am confused about Exception handling in Squeak.  Were 
> can I find 
> an adaquate description of how it works.  For instance what generates 
> which exceptions?
> 
> Q3.  How can I detect an underflow/flow in the system.  This may seem 
> like an odd question, but it comes in reference to some code that I 
> found in "Object-Oriented Implementation of Numerical Methods" by 
> Besset.  He was working in Visual Age, so his exception handling is 
> different, but the idea is to cause an overflow by repetitive 
> multipilication:
> 
> computeLargestNumber
>     | one floatingRadix fullMantissaNumber |
>     one _ 1 asFloat.
>     floatingRadix _ self radix asFloat.
>     fullMantissaNumber _ one - (floatingRadix * self 
> negativeMachinePrecision).
>     largestNumber _ fullMantissaNumber.
>     [[fullMantissaNumber _ fullMantissaNumber * floatingRadix.
>     largestNumber _ fullMantissaNumber.
>     true] whileTrue: [ ].
>     ] when: ExAll do: [:signal | signal exitWith: nil].
> 
> I tried using this code and changing the exception handling to an 
> ifError: message, but that does not work.  If i print the 
> largestNumber 
> to the transcript after each iteration the number eventually becomes 
> "Infinity", but no exception is thrown.  Instead the 
> following seems to 
> do the trick:
> 
> computeLargestNumber
>     | one floatingRadix fullMantissaNumber |
>     one _ 1 asFloat.
>     floatingRadix _ self radix asFloat.
>     fullMantissaNumber _ one - (floatingRadix * self 
> negativeMachinePrecision).
>     [largestNumber _ fullMantissaNumber.
>     fullMantissaNumber _ fullMantissaNumber * floatingRadix.
>     fullMantissaNumber isInfinite] whileFalse
> 
> Also, I was wondering what the heck Infinity is.  If one does 
> a 'Float 
> inspect' and looks at the 'classPool', they will see that 
> Infinity is a 
> class variable of Float, but that its value is Infinity?
> 
> Thanks,
> AKH
> 
> 
> -- 
> *******************************************
> Andrew Henrick
> Department of Aerospace and Mechanical Engineering
> University of Notre Dame
> http://newton.ame.nd.edu/~ahenrick
> 
> Los Alamos National Laboratory
> Dynamic eXperimentation Division 2
> Phone: 5-1137
> Mail Stop: SM C920
> 
> "Ah, I know the lion by his paw!"
>   - Johann Bernoulli after Newton discovered the solution to the
>     brachistochrone problem
> 
> "If we knew what it was we were doing, it would not be called 
>  research, would it?"
>   - Albert Einstein
> 
> "When you say 'I wrote a program that crashed Windows', 
> people just stare at 
>  you blankly and say 'Hey, I got those with the system, *for 
> free*'." - 
>   - Linus Torvalds
> *******************************************
> 
>