RE: [sv-dc] 4-state vs 3-D

If we are going to use a specific value (NaN) to denote "uncertainty" in real, then there is no point in separating "value" from "certainty".

I never liked using "NaN" or some specific value to denote "unknown" for reals - it bleeds implementation details into the language.

In fact I never fully understood what "uncertain" means in the real domain - defining an X state or Z state for reals is nothing more than mapping the 4 logic states to 4 discrete real values, in which case what is the point of using reals at all, since it is just a renaming of logic?

 -- Scott

-----Original Message-----
From: owner-sv-dc@eda.org [mailto:owner-sv-dc@eda.org] On Behalf Of Kevin Cameron
Sent: Wednesday, December 08, 2010 12:13 PM
To: sv-dc@eda.org
Subject: [sv-dc] 4-state vs 3-D

4-state refers to the received values "0,1,Z,X", since 0,1 are the range of known good logic values (for a single bit), the same nomenclature doesn't really apply for real values (since there are a lot of valid discrete values).

I'd prefer to call it "3-Dimensional", the dimensions being:

  Value (logic: 1,0, real: -inf -> +inf)
  Strength (undriven = z, regardless of type)
  Certainty (uncertain logic = x, uncertain real = NaN)

Comments?

Kev.

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