...based on a monadic tree expansion: we define a single step,
which takes the current filter configuration and builds the next
filter configuration, based on a stored chain of configuration functions
The actual exhausting depth-first results just by the greedy application pattern,
and uses the stack embedded in the "Explorer" layer of TreeExplorer
..this resolves the most challenging part of the construction work;
we use the static helper functions to infer a type and construct a suitable
processing pipeline and we invoke the same helper to initialise the base class
in the ctor.
Incidentally... we can now drop all the placeholder stubs,
since we now inherit the full iterator and child explorer API.
The test now starts actually to work... we get spam and sausage!
TODO: now actually fill in the expand functor such as to pick the
concrete filter step in the chain from a sequence of preconfigured
filter bindings
...now matters start to get really nasty,
since we have to pick up an infered type from a partially built pipeline
and use it to construct the signature for a functor to bind into the more elaborate complete pipeline
this is a tricky undertaking, since our treeExplore() helper constructs
a complex wrapped type, depending on the actual builder expressions used.
Solution is to use decltype on the result of a helper function,
and let the _DecoratorTraits from TreeExplorer do the necessary type adaptations
...it should have been this way all the time.
Generic code might otherwise be ill guided to assume a conversion
from the Iterator to its value type, while in fact an explicit dereferentiation is necessary
The intention is to augment the iterator based (linear) search
used in EventLog to allow for real backtracking, based on a evaluation tree.
This should be rather staight forward to implement, relying on the
exploreChildren() functionality of TreeExplorer. The trick is to package
the chained search step as a monadic flatMap operation
we did an unnecessary copy of the argument, which was uncovered
by the test case manipulating the state core.
Whew.
Now we have a beautiful new overengineered solution
outift the Filter base class with the most generic form of the Functor
wrapper, and rather wrap each functor argument individually. This allows
then to combine various kinds of functors
...this solution works, but has a shortcoming:
the type of the passed lambdas is effectively pinned to conform
with the signature of the first lambda used initially when building the filter.
Well, this is the standard use case, but it kind of turns all the
tricky warpping and re-binding into a nonsense excercise; in this form
the filter can only be used in the monadic case (value -> bool).
Especially this rules out all the advanced usages, where the filter
collaborates with the internals of the source.
while this is basically just code code cosmetics,
at least it marks this as a very distinct special case,
and keeps the API for the standard Filter layer clean.
a quite convoluted construct built from several nested generic lambdas.
When investigated in the debugger, the observed addresses and the
invoked code looks sane and as expected.
The intention is to switch from the itertools-based filter
to the filter available in the TreeExplorer framework.
Thus "basically" we just need to copy the solution over,
since both are conceptually equivalent.
However...... :-(
The TreeExplorer framework is designed to be way more generic
and accepts basically everything as argument and tries to adapt apropriately.
This means we have to use a lot of intricate boilerplate code,
just to get the same effect that was possible in Itertools with
a simple and elegant in-place lambda assignment
Fillter needs to be re-evaluated, when an downstream entity requests
expandChildren() onto an upstream source. And obviously the ordering
of the chained calls was wrong here.
As it turns out, I had discovered that necessity to re-evaluate with
the Transformer layer. There is a dedicated test case for that, but
I cut short on verifying the filter in that situation as well, so
that piece of broken copy-n-paste code went through undetected.
This is in fact a rather esoteric corner case, because it is only
triggered when the expandChildren() call is passed through the filter.
When otoh the filter sits /after/ the entity generating the expandChildren()
calls, everything works as intended. And the latter is the typical standard
usage situation of an recursive evalutation algorithm: the filter is here
used as final part to drive the evaluation ahead and pick the solutions.
There is a bug or shortcoming in the existing ErrorLog matcher implementation.
It is not really difficult to fix, however doing so would require us to intersperse
yet another helper facility into the log matcher. And it occurred to me, that
this helper would effectively re-implement the stack based backtracking ability,
which is already present in TreeExplorer (and was created precisely to support
this kind of recursive evaluation strategies).
Thus I intend to switch the implementation of the EventLog matcher from the
old IterTool framework to the newer TreeExplorer framework. And this intention
made me re-read the code, fixing several comments and re-thinking the design
seemingly my quick-n-dirty implementation was to naiive.
We need real backtracking, if we want to support switches
in the search direction (match("y").after("x").before("z")
Up to now, I have cheated myself around this obvious problem :-/
Greedy wildcard match .+ is unnecessary, since in case of a positive match,
the next given expression always follows immediately. We just want to skip
over some "syntactic noise"
This change makes the matching time linear in the size of the log.
But unfortunately, I still occasionally see an Segmentation Fault.
It seems to arise when compiling the regular expresions
e.g. the following RegExps cashed (right in the middle of the test)
after.+?_ATTRIBS_.+?ins.+?53 of 57 ≺358.gen010≻.+?mut.+?53 of 57 ≺358.gen010≻.+?ins.+?borgID.+?358.+?emu.+?53 of 57 ≺358.gen010≻
after.+?_ATTRIBS_.+?ins.+?53 of 63 ≺178.gen028≻.+?mut.+?53 of 63 ≺178.gen028≻.+?ins.+?borgID.+?178.+?emu.+?53 of 63 ≺178.gen028≻
after.+?_ATTRIBS_.+?ins.+?53 of 59 ≺498.gen038≻.+?mut.+?53 of 59 ≺498.gen038≻.+?ins.+?borgID.+?498.+?emu.+?53 of 59 ≺498.gen038≻
after.+?_ATTRIBS_.+?ins.+?53 of 60 ≺223.gen003≻.+?mut.+?53 of 60 ≺223.gen003≻.+?ins.+?borgID.+?223.+?emu.+?53 of 60 ≺223.gen003≻
after.+?_ATTRIBS_.+?ins.+?53 of 78 ≺121.gen015≻.+?mut.+?53 of 78 ≺121.gen015≻.+?ins.+?borgID.+?121.+?emu.+?53 of 78 ≺121.gen015≻
This finishes the first round of design drafts in this area.
Right now it seems difficult to get any further, since most of
the actual view creation and management in the UI is not yet coded.
The boost::hash documentation does not mention a significant change in that area,
yet the frequent collisions on identifiers with number suffix do not occur anymore
in Boost 1.65
On rare occasions, the test thread itself consumes faster than the producer threads feed new test data.
Make sure the test does not hangin such a situation
The original goal for #1129 (ViewSpecDSL_test) is impossible to accomplish,
at least within our existing test framework. Thus I'll limit myself to coding
a clean-room integration test with purely synthetic DSL definitions and mock widgets
...still quite braindead, but allows at least to cover the standard case as well.
A better mock element access service would at least traverse a GenNode-Tree,
and thus emulate the behaviour of the real service; yet both seems way beyond
scope right now, and all I need is some basic coverage of the Interface
My understanding is that in the standard use case, we precisely know what to expect
and just go ahead and perform the conversion. Thus it is pointless to introduce
fine grained distinctions. When the access fails, this always indicates some broken
application logic, and just raises an error.
With this solution, somewhere deep down within the implementation
the knowledge about the actual result type would be encoded into
the embedded VTable within a lib::variant. At interface level,
ther will be a double dispatch based on that result type
and the desired result type, leading either to a successful
access or an error response.
