I don't really understand HDL/Verilog, but I've worked with people who do. In fact, I even wrote a pre-processor that transformed the same DSL to Python, C++, and Verilog.

In my mind, the HDL use case is FAR too narrow and specialized to warrant a new arrow operator, let an entirely new parser and semantics around arbitrary operators. There are several existing dunders that could plausibly be repurposed already (<<, <<=, <=, etc). Those might look sightly different than the verilog operators, but that's a very small price. In fact, just using attributes and assignment is an incredibly low bar too, and allows whatever overriding you wish.

I just don't buy the idea that such a DSL can only be useful if it spells 'abc <== message' and useless if it spelled the same thing as 'abc <<= message'.


On Fri, May 24, 2019, 9:06 AM Yanghao Hua <yanghao.py@gmail.com> wrote:
On Fri, May 24, 2019 at 12:29 PM Greg Ewing <greg.ewing@canterbury.ac.nz> wrote:
>
> Yanghao Hua wrote:
> > I have explained the problem of use
> > descriptors in previous replies, where you cannot have a local signal,
> > e.g. obj.signal = thing # works, but local_signal = thing # doesn't
> > work.
>
> Maybe you could do something like:
>
>     local = Signals()
>     local.signal1 = ...
>     local.signal2 = ...

In structure design ... and especially when you design a hardware that
is meant to be automatically converted into verilog or even logic
gates, I personally would really want to have a one-to-one
relationship of the python-objects vs the actual hardware structures.
The granularity is at signal/bit level. This is why I really think
giving a special assignment in python which users could override is
really helpful, rather than having to have this kind of special case:
if you do "self.abc = thing" descriptor mechanism is invoked, but the
very next line if you do "abc = thing" ... nothing will happen. This
special case can be completely removed and having a much better
conceptual consistency if the "<==" assignment operator always behaves
the same, doesn't matter if it is "self.abc <== thing" or "abc <==
thing".
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