execution context: Make submission time parameters available without serializing the parameter callable

[ghost]

When you create a submission time parameter in Python and want to use this in an operator Callable/Lambda expression, you would do following:

threshold = topology.create_submission_parameter('threshold', 100);

# s is some stream of integers
s = ...
s = s.filter(lambda v : v > threshold())

Current restriction is, that these callables (here threshold) cannot be used in functions. Instead of passing around callable instances you may want to use submission time values in callables similar the way to anyone can make a call to get at environment variables.

[ghost]

One solution would be to implement a function streamsx.ec.get_submission_time_value(name, type_=None)

The restrictions and the interworking with submission time parameters created with SPL expressions must be documented.