Re: [Help-smalltalk] Works in Squeak but not GNU (deepCopy?)

[Paolo Bonzini]

On 11/18/2011 01:42 PM, Jimmy Johnson wrote:
> I don't know where else to turn for help so...if one of you experts
> would have the time to look at this project and see if an obvious
> problem jumps out, and let me know, I would really appreciate it.
>
> The project is to write a rational number class and include
> units/dimensions (meters/length).  The system works fine in Squeak
> SmallTalk, but fails in gnu SmallTalk.  I'm guessing it has something
> to do with my use of deepClone.

Yes, that's correct.  deepCopy is not standardized, but it traditionally 
made only a 1-level deep copy.

The better way to do it in GNU Smalltalk is to use "copy" and add 
postCopy methods such as

Unitable>>postCopy
        unitsImp := unitsImp collect: [ :each | each copy ]

DimensionedRational>>postCopy
        unitsImp := unitsImp copy
        
etc.

From a quick read of the code I'm not sure where you actually need 
deeper copies, so the above is likely incomplete or incorrect.

As an aside, I suggest that you replace all uses of "self length" with 
simply "1" (why is length special?) and merge the Constants and 
Dimensionable classes.  Also, the Comparable class is exactly the same 
as Magnitude, except that it doesn't test the precondition that the 
classes are the same.  In general such preconditions hamper the usage of 
polymorphism, so they're not used in Smalltalk.

Paolo