Re: [myhdl-list] strange problem

[Neal B. <ndb...@gm...>]

Jan Decaluwe wrote:

> Neal Becker wrote:
>> I'm still trying to wrap my head around myhdl.  This one is weird.
> 
> It is purely a Python scope issue. Consider:
> 
> def f():
>     n = 0
>     def g():
>             n += 1
>             print n
>     g()
> 
> f()
> 
> Running this gives:
> 
>> python tmp.py
> Traceback (most recent call last):
>   File "tmp.py", line 8, in <module>
>     f()
>   File "tmp.py", line 6, in f
>     g()
>   File "tmp.py", line 4, in g
>     n += 1
> UnboundLocalError: local variable 'n' referenced before assignment
> 
> 
> To understand what happens, consider that 'n += 1' is equivalent to:
>   n = n + 1
> 
> When you *assign* to n somewhere locally, Python considers it a
> local variable. As the n in the rhs as not been locally assigned yet,
> you get the error.
> Note that as long you don't assign to n, you would have read
> access to the n in the enclosing scope.
> 
> For your case, put the initialization in the generator before
> the while loop.
> 
> Jan
That worked fine, until I needed to access (read) a variable also in another 
generator.

I find that:

x = Signal (0)

def gen1...
  x.next = x + 1

def gen2...
  print x

Works fine, but if x was just a simple variable, say int, we have the 
referenced before assignment (of course, using x = x+1 instead of x.next = 
x+1).

Other than using a Signal, any other solution?  It seems silly to use Signal 
for something that is just part of my test setup.