The array filter test (modules/database/test/std/filters/arrTest.cpp)
creates "double" array filters that look like:
{"arr":{},"arr":{"s":x,"e":y,"i":z}}
Apparently this is interpreted by EPICS base to mean two array filters
in succession, first the left, then the right.
According to the JSON standard this is allowed. But is it a good idea?
Are there practical use cases? (The test where I've seen this doesn't
count IMO).
As far as I recall (that was 8 years ago, and Michael wrote the tests), that test verifies that the array filter functionality works inside a filter chain, i.e., with with another filter providing the input data, not a record.
The easiest way to achieve that without adding another dependency is to use two array filters in a chain. I don't think this test was driven by a specific use case.
Cheers,
~Ralph
