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MathGroup Archive 2005

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The question of equality,...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60486] The question of equality,...
  • From: terryisnow at yahoo.com
  • Date: Sat, 17 Sep 2005 02:32:32 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Ok I thought I understood this stuff but maybe not,...

If I wanted to check for bit-for-bit equality of two
arbitrary precision numbers (without regard to how
many of those digits are meaningful) like the way it
would be done using the "==" operator in C, then
neither "==" nor "===" will do the job, is that
correct?

For "==" the 5.1 Appendix A says:

"Approximate numbers are considered equal if they
differ in at most their last eight binary digits
(roughly their last two decimal digits)."

For "===" the 5.1 Appendix A says:

"SameQ requires exact correspondence between
expressions, except that it considers Real numbers
equal if their difference is less than the uncertainty
of either of them"

So what can I use then?

Any and all help is much appreciated.

Terry


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