resolved integers (was RE: [vhdl-200x] Update to proposal for arbitrary integers)

From: Martin.J Thompson <>
Date: Tue Oct 14 2014 - 05:09:01 PDT
From: [] On Behalf Of David Bishop

A “NaN” is a very specific value for a floating point number.   An exponent of all “1” (which means infinity) and a fraction which starts with a “1”.     Since all of the bits in an integer are valid, I don’t know how you would do an invalid number.   You can’t just pick one because somebody will need to use it.

I agree – if you want an ‘undriven value’, then it has to be separate.  The simulator could track it in whatever softwarey way suits, say via an internal variable with a bit for each resolved integer object which needs to be tracked.  In synthesis, a resolved integer could an extra bit to signifiy its “drivenness”.

Or either level of tool could allocate a value outside of the valid range for the integer in question (to use internally as a flag), which could be accessed through the language via some suitable abstraction.

At this stage, I would propose that Daniel could write up a requirement on the Twiki for what he would like to happen (without implementation details at this stage?) and we can add it to the future discussions...


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