Re: [myhdl-list] intbv.signed()

[Jan D. <ja...@ja...>]

Günter Dannoritzer wrote:
> Hi,
> 
> I was gonna try out implementing the signed() function to intbv.
> 
> My first question is whether it should be a function or a property? What
> would be the decision about what to take. For example with the min and
> max values they are implemented as property. As there are no parameters
> needed, could the signed by also implemented as property?

To me, a property contains some static info about an existing object (even when
it is implemented as a method behind the curtains), while a method returns
some new object. So, it should be a method. The brackets indicate that
"something is being done".

> My next question is what signed() will return. Just the value as integer
> or will it be an intbv instance with the range set based on the _nrbits,
> but as +/- range?

I would go for an integer to start with. That is what MyHDL does now for
many operators. It is more efficient than constructing intbv's (although
I dont' know how much more) and seems sufficient in many cases. Note that
when we write:

a[:] = <some expression>

the range checking problem is transfered to the left-hand side.

Some other (more bit-oriented) operators return an unconstrained intbv
and we could do this also if there's a good reason. But I would
avoid trying to infer ranges.

Jan

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