How to do Nonblocking writes of unhashable data: Alternation([{ (c, unhashable): None }])

[Peter Waller]

How do I use an alternation with unhashable data, such as a
dictionary?

I wrote the following function, but it doesn't work if `what` is
unhashable. Is there another obvious way to achieve what I want?

def nonblock_write(comm_channel, what):
"""
Tries to write `what` to `comm_channel`.
returns True on successful write
"""
chan, msg = P.Alternation([
{ (comm_channel, what): None },
{ P.Skip(): None },
]).execute()

return chan == comm_channel

TIA.
- Peter

[Peter Waller]

A quick read of the pycsp code made it obvious that one can also do:

   chan, msg = P.Alternation([
       (comm_channel, what, None),
       { P.Skip(): None },
   ]).execute()

Which is functionally equivalent but doesn't have this limitation.

Thanks anyway.

[Rune Møllegaard Friborg]

This is a problem with the original syntax.

The new syntax:
chan, msg = P.AltSelect(P.OutputGuard(comm_channel, msg=what), P.SkipGuard())

Look at the examples in trunk for inspiraition.

Mvh.
Rune M. Friborg

[Peter Waller]

2010/10/1 Rune Møllegaard Friborg <ru...@diku.dk>

This is a problem with the original syntax.

The new syntax:
chan, msg = P.AltSelect(P.OutputGuard(comm_channel, msg=what), P.SkipGuard())

Look at the examples in trunk for inspiraition.

Oh, I thought I was looking at the new syntax - I was going by the "PyCSP Revisited" document.