Fast long overflow detection?

[Mark Roos]

So I thought I could get away with 64bit ints and not implement the 
Smalltalk automatic conversion
to BigIntegers.  Bad plan.

So I went ahead and did it while I waited for the super bowl to start. Not 
too difficult.  Just wrappered
java BigInteger and added some simple overflow detection.

But I am concerned about the impact on integer ops by adding a pretty 
complex precalc overflow detection.
To help I decided to limit small ints to 62 bits and defer some checking 
until after the op and cache lookup.

Any suggestions on approaches that offer superior techniques?

Seems like a methodHandle of guardOverflow would be handy someday.

regards
mark
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