not sure yet if any of this works, because the
technicalities of dealing with variadic types are
quite different to our LISP-style typelist processing.
The good news is that with variadic templates it is
indeed possible, to supply dynamically picked arguments
to another function taking arbitrary arguments.
This all relies on the feature to unpack argument packs,
and, more specifically, about the possiblity to "wrap"
this unpacking around interspersed function call syntax
template<size_t...i>
Xyz
do_something(MyTuple myTuple)
{
return Xyz (std::get<i> (myTuple) ... );
}
Here the '...' will be applied to the i... and then
the whole std::get-construct will be wrapped around
each element. Mind bogging, but very powerful
we made double use of our Tuple type, not only as a
generic record, but also as a metaprogramming helper.
This changeset replaces these helpers with other
metafunctions available for our typelists or type sequences
(with the exception of code directly related to Tuple itself,
since the intention is to delete this code alltogether shortly)
there was a muddeled mix of type lists and type sequences,
and both where used for processing. Probably the origin
of that confusion was the design of our own Tuple class,
which is implemented based on typelists but accepts a
type sequence at the front-end. From there, a confusing
pattern of equivalence between lists and sequences emerged,
leading to several functions accepting "anything".
This misdesign is not eradicated yet, but in this specific
instance here, has cost me several hours to pinpoint a bug
introduced while refactoring.
See also #967 and #301
This definition -- together with the already existing specialisation
in typeseq-util, allows always to rebind from a given type-list back
to the corresponding type-sequence, by accessing the type member `Seq`
...which causes problems when a preceding include
has already dragged in <functional>
the actual problem is the std::hash hack, which probably
is even no longer possible and could be removed (but
I don't have the time to investigate this somewhat
tricky topic right now)
To prevent this confusing situation, I'm adding the
include of "lib/symbol.hpp", to ensure we do have
the actual definitions of string and Literal,
which trait.hpp just declares forward.
An note, lib/symbol.hpp also includes hash-standard.hpp
first, so we avoid triggering problematic situation
from a header (format-cout.hpp), which is pervasively used
all over the place....
basically this comes down to provide some convenience fixture
within the test::Nexus, which automatically generates and wires
mock commands.
Not sure if this is even possible to the extent envisioned here
since our test.sh runner can be used to verify the
expected output printed by tests, working with these
output transcripts of larger tests can be hard at times.
These separators help to find who produced which output
and they prevent a regexp match to grep beyond the feed
of a single function (which can be a common problem
when using the self-diagnostic output of the facility
currently in test, which obviously will be similar
on any data printed.
- replace remaining usages of typeid(T).name()
- add another type simplification to handle the STL map allocator
- clean-up usage in lib/format-string
- complete the unit tests
- fix some more bugs
quite sure I never really meant to do that, just, at that time,
it seemed logical to treat Placement as yet another smart-ptr.
But in the light of what crucial entity Placement became meanwhile,
I can't imagine a single case where anyone wants to wrap away a
placement as if it was some shrink-wrap
turns out this is a tricky situation.
We want to accept pretty mutch everything, yet we want to get a grip
on anything object-like, so to reveal available RTTI information.
Now, given the way C++ template substitution works, the 'TY const&' overload
wins with only a few exceptions. The reason is, C++ invokes most functions
passing the concrete argument as reference, unless this is not possible,
because the concrete artument is a rvalue. The automatic reduction of
reference expressions does the rest. Consequently the overload with 'const&'
turns out to be the best match even when we invoke the function with a
pointer expression, which would then be made into a pointer-to-a pointer
by our forward call.
There are two remedies for this dilemma:
- make the second overload just typeStr (TY&)
- explicitly remove the second overload for pointers
The first solution unfortunately would rule out passing of anonymous
objects like concatenated strings; in fact it would rule out passing
rvalues as such. While the second solution, chosen here, works really
for everything, and also has the nice side effect of stripping away
any const, pointer and reference adornements elegantly before we
even start to analyse the type.
The only downside of this solution is that it looks intimidating
to the casual reader. Well, I'd say, get used to it.
over time, we got quite a jungle with all those
shome-me-the-type-of helper functions.
Reduced and unified all those into
- typeString : a human readable, slightly simplified full type
- typeSymbol : a single word identifier, extracted lexically from the type
note: this changeset causes a lot of tests to break,
since we're using unmangeled type-IDs pretty much everywhere now.
Beore fixing those, I'll have to implement a better simplification
scheme for the "human readable" type names....
...based on all the clean-up and reorganisation done thus far,
we're now able to rebuild the util::str in a more direct and
sane way, and thus to disentangle the header inclusion problem.
due to the new automatic string conversion in operator<<
the representation of objects has changed occasionally.
I've investigated and verified all those incidents.
...other than intended, the bomb did explode on random occasions,
with an probability of about 4% (when rr >= 96).
Btw, there was also the mistake to throw an heap allocated
object by pointer. Damn Java habits.
- remove unnecessary includes
- expunge all remaining usages of boost::format
- able to leave out the expliti string(elm) in output
- drop various operator<<, since we're now picking up
custom string conversions automatically
- delete diagnostics headers, which are now largely superfluous
- use newer helper functions occasionally
I didn't blindly change any usage of <iostream> though;
sometimes, just using the output streams right away
seems adequate.
the usual drill...
only when wrapped into a factory function, RAII is really
airtight, even when used from within expression evaluation.
Thanks C++11 we're now able to provide such en passant
our lib::P smart-pointer is built on top of std::shared_ptr,
while additionally delegating comparisons to the pointee.
In a similar vein, I've now added a custom string conversion,
delegating to the pointee, with a type-string as fallback.
Together with the built-in string conversion for output streams,
we should now be able to remove most of the explicit string
conversions and calls to util::str in all of our test code.
This removes the last roadblock towards disentangling the
pretty-printing header includes, which in turn should allow
us to remove any conditional code in the built-in string
conversion of GenNode, Variant and the like. Which basically
was the objective for ticket #985
use a shortened display, showing only the last 4 bytes for diagnostics
since we're typically only interested in spotting "same" and "different",
while the full memory address is irrelevant
provide a generic overload for the stream inserter operator<<
to use custom string conversions when applicable.
The overload will be disabled when a direct lexical conversion
is possible (which means, we can expect the output stream to
know allready how to print those values, like e.g. all kinds
of numbers).
Additionally, we provide a pretty-printing mechansim for pointers,
to show the address and possibly invoke a custom string conversion
on the pointee
No more fiddling with printf just to show a number reliably!
simple functions to pretty-print addresses,
doubles and floats (fixed-point, with rounding).
Also make all these basic formatting helpers noexcept
- simple function to pick up the mangled type
- pretty-printing is implemented in format-obj.cpp
- also move the demangleCxx()-Function to that location,
it starts to be used for real, outside the test framework
our minimal compiler requirement is gcc-4.9 since the
transition to Debian/Jessie as reference system.
gcc-4.9 is known to treat SFINAE on private fields properly
this is a stripped-down and very leightweight variant
of the well-known enable_if metaprogramming trick.
Providing this standard variant in a header with minimal
dependencies will allow us to phase out boost inclusions
from many further headers. As a plus, our own variant
is written such as to be more conciese in usage
(no "typename" and no acces of an embedded "::type" menber)
this includes a reorganisation concept for the header includes,
a minimal version (with minimal include dependencies), and
a generic ostream inserter operator<<
...and learned a lot about the new type_traits on the way.
As it seems, it is not possible to get a clean error message
when passing an "object" with no custom string conversion;
instead, some overload for an rvalue-ostream kicks in.
probably I'll go for shoing a type string in these cases
now we use boost::format through our own front-end util::_Fmt
solely, which both helps to reduce compilation time and code size,
and gives us a direct string conversion, which automatically
uses any custom operator string() available on arguments.
While desirable as such, I did this conversion now, since
it allows us to get rid of boost::str, which in turn helps
to drill down any remaning uses of our own util::str
the fixed version is actually more permissive,
insofar it matches any type of event, when ID = classifier
(or alternatively it matches events with type = classifier)
our formatting helper for diagnostics output,
which is primarily used in the unit-tests,
first tries to invoke a custom string conversion.
If that is not possible, it falls back to printing
the demangled type name of the object in question.
With just a minor change we're able to evaluate RTTI here
and print the actual type name, instead of the static
supertype the compiler sees on invocation. We just rely
on the typeid(obj) built-in function.
The only catch is we have to strip the " const*" suffix
(and no, it is not possible to do that on metaprogramming
level, due to the special situation where we have a void*)
This also prompted me to write some util functions for
this often encountered task to check / remove a prefix or suffix
Hopefully I've got those functions correct and safe....
...this is necessary whenever the mocked facility covered
by log matching is managed automatically as singleton,
because then other test cases will leave garbage
in the log
I worked under the erroneous assumption, that Doxygen
will use its internal entity-IDs as the link-IDs when
generating mardown-links. Yes, this seemed logical and
this would be the way I'd implement it....
But seemingly, Doxygen is not so consistent when it
comes to questions of syntax. The same holds true for
markdown, which lacking a coherent definition anyway.
Another problem is that Doxygen's auto-link generation
frequently fails, for reasons not yet clear to me.
Sometimes it seems to be necessary to give it a nudge
by including the \ref command. While I'm not willing
to go into focussed invstigation of Doxygen syntax
right now, at least I've done a search-and-replace
to remove the malformed links I've written the
last days
the initial draft of this concept is in place now, and
the first round of unit tests pass. I've got some understanding
of the purpose of the interactions and involved elements
and I'm confident this design is evolving in a sane way.
Note: extensive documentation is in the TiddlyWiki,
here I've just pasted and reworded some paragraphs from there
and integrated them into the Doxygen docs
Explanation: sigC++ was already linked as transitive dependency
from gtkmm, since it is used for the "signal-slot" system wihin GTK.
But now we want to use sigC++ itself from our generic UI-Backbone,
so we need to pick up the additional compiler and linker flags
and use them when building the relevant parts of both the application
and the test suite
at the point when we're connecting a new node to the UI-Bus,
the new node's BusTerm is not yet initialised, since we need
the uplink connection we're about to create for setting up
this BusTerm.
Consequently, the new nodes's ID is not yet initialised,
so we need to pass this endpoint-ID explicitly to the
registration function.
since, by definition, the Nexus is "the" up-link,
all we need is clever overriding of the relevant
handling functions, so the nexus will care for the routing,
while the CoreService cares for command and presentation
state handling
next step will be to rig the mock element and set up
and cover the basic / generic element behaviour
This changeset
- adapts the (planned) unit test to the semantic of
the EventLog, which is now fully implemented
- adjusts the function names on the public Tangible interface,
to be better in line with the naming convention of the
corrsponding operations on the UI-Bus:
* "mark" operations are towards the UI element
* "note" messages are from the UI element towards some
state manager, which can be reached via the bus
so this turned out to be rather expensive,
while actually not difficult to implement.
On the way, I've learned
- how to build a backtracking matcher, based on
a filtering (monadic) structure and chained lambdas
- learned the hard way how (not) to return a container
by move-reference
- made first contact with the regular expressions
now available from the standard library
this function is of use also for creating a vector of strings
from a bunch of C-Strings, but it could also be used to
construct other stuff initialised by strings (e.g. RegExps)
this deals with a recurring problem in test code:
very common "simple" fractional values can not be represented
precisely as binary floating point. The classical example is 0.1
Since this is a diagnostics facility, we can cheat around this
insidious problem by just setting a limited rendering precision.
Floating point numbers behave deterministic; you just need
to know how to deal with limited precision.
abandon the use of an assertion exception to signal match failure,
rather use a final bool conversion to retrieve the results.
Error messages are now delivered by side effect into STDERR
The reason is we're unable to deliver the desisred behaviour
with the chosen DSL syntax in C++ ; on a second thought the
new approach is even better aligned with the overall way
we're writing tests in Lumiera. And we produce match-trace
messages to indicate the complete matching path now
implemented a solution to determine negative matches.
But because this solution relies on throwing from a destructor,
it is not possible to catch the resulting assertion failure.
Not sure why (AFAIK there is no second exception thrown
while unwinding the stack), but throwing from dtors is
considered "undefined behaviour" anyway.
So this solution is of limited use
beyond that solution, I'm not sure if the desired syntax
can be implemented at all in C++. Seems that we need to build
a bracketing construct, first to initiate a negated match
and finally, after all queries, to detect if there happened
any failure or not
...no need to enclose empty sections when there are no
attributes or no children. Makes test code way more readable.
TestEventLog_test PASS as far as implemented
...and fix an error (header include order of diagnostics facility)
which prevented the first matcher implementation to work
the after()-match now works as expected
this is the tiny bit of operational functionality needed on top:
whenever we're reconfiguring the predicate, we need to re-trigger
the evaluation (and clear the cached value)
n.b.: I've verified in debugger that the closure is
allocated on the heap and the functors are passed by value
after looking into our various iterator tools,
it seems obvious that our filtering iterator implementation
has almost all of the required behaviour; we only need to
add a hook to rewrite and extend the filtering functor,
which can now nicely done with a lambda closure.
This means all memory management, if necessary, is
pushed into std::function and the automated memory
management for closures provided by the runtime.
...providing the standard implementation of UI-Bus connectivity.
It seems reasonable to place all of the UI-Bus implementation into
a single translation unit
what you see here now is just the tip of the icebearg...
If we follow this route, the Lumiera UI will become way more
elaborate and responsive than average desktop applications
..while we should note at this point that the whole techique
of hijacking std::hash is superfluous now, since the standard libray
does no longer define a static assertion which defeats SFINAE
some tests rely on additional diagnostics code being linked in,
which happens, when lib/format-util.hpp is included prior to
the instantiation of lib::diff::Record rsp. lib::Variant.
The reason why i opended this can of worms was to avoid includion
of this formatting and diagnostics code into such basic headers
as lib/variant.hpp or lib/diff/gen-node.hpp
Now it turns out, that on some platforms the linker will use
a later instantiation of lib::Variant::Buff<GenNode>::operator string
in spite of a complete instantiation of this virtual function
being available already in liblumierasupport.so
But the real reason is that -- with this trickery -- we're violating
the single definition rule, so we get what we deserved.
TODO (Ticket #973): at a later point in development we have to re-assess,
the precise impact of including lib/format-util.hpp into
lib/diff/gen-node.hpp
Right now I expect GenNode to be used pervasively, so I am
reluctant to make that header too heavyweight.
preliminary workaround for Ticket #972
On Debian/Jessie, we observed the following error
"gtk-lumiera.css:38:19Theming engine 'adwaita' not found"
even though the package gnome-themes-standard *is* installed
This allows at least to bring the UI up, even if loading
our custom theme and stylesheet fails.
This is a development snaphot pre release of Lumiera.
It features codebase maintenance, upgrade to C++14 and GTK-3
and some work towards a Proc-GUI connection (unfinished)
Update README, AUTHORS, LICENSE and similar release docs.
because otherwise we'd need to send a whole subtree
over the wire and then descend into it just to find an element.
This too is a ripple effect of making '==' deep
well... this was quite a piece of work
Added some documentation, but a complete documentation,
preferably to the website, would be desirable, as would
be a more complete test covering the negative corner cases
yeah, working with open fire is dangerous...
For performace reasons I've undercut the premise
to make GenNode / Record immutable. Now I'm dealing with
raw storage layout together with this quite hairy distinction
between "attribute scope" and "child scope"
In hindsight, it might have been better to implement Record
as a single list, and to maintain a shortcut pointer to jump
to the start of the attributes.
while implementing this, I've discovered a conceptual error:
we allow to accept attributes, even when we've already entered
the child scope. This means that we can not predictable get back
at the "last" (i.e. the currently touched) element, because this
might be such an attribute. So a really correct implementation
would have to memorise the "current" element, which is really
tricky, given the various ways of touching elements in our
diff language.
In the end I've decided to ignore this problem (maybe a better
solution would have been to disallow those "late" attributes?)
My reasoning is that attributes are unlikely to be full records,
rather just values, and values are never mutated. (but note
that it is definitively possible to have an record as attribute!)
...while I must admit that I'm a bit doubtful about that
language feature, but it does come in handy when manually
writing diff messages. The reason is the automatic naming
of child objects, which makes it often hard to refer to
a child after the fact, since the name can not be
reconstructed systematically.
Obviously the downside of this "anonymous pick / delete"
is that we allow to pick (accept) or even delete just
any child, which happens to sit there, without being
able to detect a synchronisation mismatch between
sender and receiver.
i.e. flat match, not deep equality.
This allows to send just an Ref (with the ID) over the
wire to refer to an complete object to be picked, moved
or deleted on the receiver side.
in the first version, I defined equality to just compare the IDs
But that didn't seem right, or what one would expect by the concept
of equality (this is a long standing discussion with persistent
object-relationally mapped data).
So I changed the semantics of equaility to be "deep".
As this means possiblty to visit a whole tree depth-first,
it seems reasonable to provide the shallow "identity-comparison" likewise.
And the most reaonable choice is to use the "matches(object)" API
for that, since, in case of objects, the matches was defined
as full equality, which now seems redundant.
Thus: from now on: obj.matches(otherObj)
means they share the same IDs
The Ref-GenNode is just a specifically constructed GenNode,
and intended to be sliced down to an ordinary GenNode
immediately after construction. It seems, GCC didn't "get that"
and instead emitted an recursive invocation of the same ctor,
which obviously leads to stack overflow.
Problem solved by explicitly coding the copy initialisation,
after the full definition of Ref is available.
the type is the only meta attribute supported by now,
thus the decision was to handle this manually, instead of
introducing a full scope for meta attributes. Unfortunately
this leads to an assymetry: while it is possible to send an
attribute named "type", which will be intercepted and used
as a new type ID, the type will not show up when iterating
or searching through attributes.
When applying a diff, the only possibility is to *insert*
a new type attribute, and we need to check and handle this
likewise manually.
It is difficult to reconcile our general architecture for the
linearised diff representation with the processing of recursive,
tree-like data structures. The natural and most clean way to
deal with trees is to use recursion, i.e. the processor stack.
But in our case, this means we'd have to peek into the next
token of the language and then forward the diff iterator
into a recursive call on the nested scope. Essentially, this
breaks the separation between receiving a token sequence and
interpretation for a concrete target data structure.
For this reason, it is preferrable to make the stack an
internal state of the concrete interpreter. The downside of
this approach is the quite confusing data storage management;
we try to make the role of the storage elements a bit more
clear through descriptive accessor functions.
implement the list handling primitives analogous to the
implementation of list-diff-applicator -- just again with
the additional twist to keep the attribute and child scopes
separated.
...so now the stage is set. We can reimplement
the handling of the list diff cases here in the context
of tree diff application. The additional twist of course
being the distinction between attribute and child scope
each language token of our "linearised diff representation"
carries a payload data element, which typically is the piece
of data to be altered (added, mutated, etc).
Basically, these elements have value semantics and are
"sent over wire", and thus it seems natural when the
language interpreter functions accept that piece of payload
by-value. But since we're now sending GenNode elements as
parameter data in our diff, which typically are of the
size of 10 data elements (640 bit on a 64bit machine),
it seems more resonable to pass these argument elements
by const& through the interpreter function. This still
means we can (and will indeed) copy the mutated data
values when applying the diff, but we're able to
relay the data more efficiently to the point where
it's consumed.
this boils down to the two alternatives
- manipulate the target data structure
- build an altered copy
since our goal is to handle large tree structures efficiently,
the decision was cast in favour of data manipulation
so basically it's time to explicate the way
our diff language will actually be written.
Similar to the list diff case, it's a linear sequence
of verb tokens, but in this case, the payload value
in each token is a GenNode. This is the very reason
why GenNode was conceived as value object with an
opaque DataCap payload
while it's still not really clear how we'll use this helper
and if we need it at all -- some weeks ago I changed its
semantics to be strictly based on the delta to a reference level.
Now this means, we could go below level zero, but this doesn't
make any sense in the context of navigating a tree. Actually,
our test case triggered this situation, which caused the
reference level to wrap around, since it is stored in an
unsigned variable.
Thus I'll add a precondition to keep the level positive,
and I'll change the test to comply.
Initially I've deliberately omitted those, to nudge towards
using time quantisation and TCode formatting for any external
representation of time values.
While this recommendation is still valid, the overloaded
string conversion turns out to be helpful for unit testing
and diagnostics in compound data structures.
See Record<GenNode>
initially the intention was to include a "bracketing construct"
into the values returned by the iterator. After considering
the various implementation and representation approaches,
it seems more appropriate just to expose a measure for the
depth-in-tree through the iterator itself, leaving any concerns
about navigation and structure reconstruction to the usage site.
As rationale we consider the full tree reconstruction as a very
specialised use case, and as such the normal "just iteration" usage
should not pay for this in terms of iterator size and implementation
complexity. Once a "level" measure is exposed, the usage site
can do precisely the same, with the help of the
HierarchyOrientationIndicator.
Whooa!
Templates are powerful.
programming this way is really fun.
under the assumption that the parts are logical,
all conceivable combinations of theses parts are bound to be correct
it passes compilation, but the test still fails, since
I've changed the expected semantics of the iteration,
in the light of the insights I've gained during
re-investigation of the IterExplorer.
What I now actually intend is rather to embed a
HierarchyOrientationIndicator into the iterator,
instead of returning a special "bracket" marker
reference to indicate return from a nested scope.
Only a Record payload constitutes a nested scope.
For all other (primitive) values, we return an empty iterator.
When used within ScopeExplorer, this implementation will just
lead to exposing any simple value once, while delving into
iteration of nested scopes
The only substantial change (besides compilation fixes) is
to confine the iteration to *const access*
This is a good thing; the whole Record/GenNode structure
was designed to represent immutable data, necessitating
a dedicated *Mutator* for any reshaping.
seemingly the operator-> was not yet used in any real scenario.
The whole point with IterAdapter is that it uses an opaque "location type",
which is owned by the controlling container. In many cases this will
actually be just a pointer into the container storage, but we
must not assume it is this way. Thus the only way to obtain a
(language) pointer is to dereference the "position type" and
take the address of the result
Initially I intended just to supply an addapter to use
the monadic IterExplorer for this recursive expansion
of GenNode contents. Investigating this approach was
relevant to highlight the minimum requirements for
such an evaluation mechanics: since our GenNode
is an hierarchical structure without back-links,
we are bound to use a stack at some point. And
since an Iterator is a materialised continuation,
we can not use the processor stack and are forced
to represent this stack in memory.
Yet, on second thought, we do not need the full power
of the IterExplorer monad; especially we do not need
to bind arbitrary functions into the monad, just one
single scope exploring function, implemented as
Variant visitor. Based on these observations, we can
"inline" the monad structure into a double nested
iterator, where the outer capsule carries a stack
of scopes to be explored.
This helper was drafted for the Job / JobPlanning and Scheduler
interface in 2013, but seemingly not yet put into action. While
in the original use case, we have a genuine measuerment for the
tree depth (given by the depth of the processing stack), in other
use cases we want to use to offset embedded within the indicator
itself for keeping track of the depth. Thus I add a second
mark operation, which usess the current offset to set a new
reference level. This has the consequence that the offset
has now to reflect the new reference point immediately
Since C++ is not a real functional programming language and
has unsafe unmanaged pointers, it is not difficult to produce
dangling references within an extended evaluation pipeline
involving transient objects and pass-by-reference.
In the initial implementation, I built in a safeguard copy
into the signature of the Explorer function, to make sure even
a transiently dressed-up input value gets materialised before
proceeding with the source sequence. Unfortunately this safeguard
turns out as a roadblock now; we might as well take the input
by reference and return an "expanded" state by value. We might
even want to do the full "expansion" on referred state, when
we're able to ensure the source values remain in memory
until consumption.
Thus now the full power of decision is placed on the signature
of the explorer function. The expansion strategies of IterExplorer
will no longer attempt to "sanitise" the signature of the passed-in
function to prevent desaster; I've added some warnings into the
documentation to highlight that danger. Basically, if you want
to be clever, then you're bound to read and understand inticacies
of the implementation.
If in doubt, use values and copying. C++ is optimised for that.
allow to pick the bare function signature from any "function like" entity
Note: we're still unsing our own Typelist construct to represent
the function argument types. Since we're now using C++11, this
could be replaced by varargs, and we could get rid of those
various overloads for different numbers of arguments.
Unfortunately this transition is linked to the usage of
argument tuples in our command framework (which could then be
replaced by std::tuple), and this is still a bit of rather
technical work, which I do not want to spend much time on
right now
remembered that some years ago I had to deal with a very similar problem
for planning the frame rendering jobs. It turned out, that the
iterator monad developed for this looks promising for our task at hand
horay!
seems like madness?
well -- found and squashed a bug: equality on RecordRef
implicitly converted to GenNode(RecordRef), which always
generates new (distinct) IDs and so never succeeds. What
we really want is equality test on the references
contrary to the Visitor, accepting a Predicate is const,
and -- of course -- the Predicate invocation returns bool.
This can be used to implement comparison operators or
search functions on Variant based data structures.
There is no generic implementation for these functions, since
they are highly dependent on the payload used within Record<TY>
Here we use Record<GenNode>, which turns the whole setup into an
recursive data type; we especially rely on the fact that each
GenNode has an embedded symbolic ID, and we use this ID to encode
the 'key' for named attributes
while in debugging, it turned out that the short type-prefix
was implemented in a too simplistic way; it fails on stuff
like 'lib::diff::Record<lib::diff::GenNode>'
while I must add, that the whole purpose of these ID functions
is somewhat unclear and needs to reveal itself as we move forward
initially my intention was to use the ID for equality test.
But on a second thought, this seemed like a bad idea, since
it confuses the concepts of equality and identity.
Note: at the moment, I do not know if we even need an equality test,
so it is provided here rather for sake of completeness. And this
means even more that we want an 'equality' implementation that
does what one would naively expect: compare the object identity
*and* compare the contents.
...while on the train back from FrOSCon.
still the same old problem: we need a better hash function
for generating our Entry-IDs. The default hash function from Boost performs
poor on strings with common prefix and trailing number.
We use a hackish workaround, which is sufficient to avoid collisions
among the first 10000 numbers.
not entirely sure about the design, but lets try this approach:
they can be "cloned" and likewise move-assigned, but we do not
allow the regular assignment, because this would enable to use
references like pointers (what we deliberately do not want)
especially setting (changing) attributes turned out to be tricky,
since in case of a GenNode this would mean to re-bind the hash ID;
we can not possibly do that properly without knowing the type of the payload,
and by design this payload type is opaque (erased).
As resort, I changed the semantics of the assign operation:
now it rather builds a new payload element, with a given initialiser.
In case of the strings, this ends up being the same operation,
while in case of GenNode, this is now something entirely different:
we can now build a new GenNode "in place" of the old one, and both
will have the same symbolic ID (attribute key). Incidentally,
our Variant implementation will reject such a re-building operatinon
when this means to change the (opaque) payload type.
in addition, I created a new API function on the Mutator,
allowing to move-in a complete attribute object. Actually this
new function became the working implementation. This way, it is
still possible to emplace a new attribute efficiently (consider
this to be a whole object graph!). But only, if the key (ID)
embedded in the attribute object is already what is the intended
key for this attribute. This way, we elegantly circumvent the
problem of having to re-bind a hash ID without knowing the type seed
initially, the intention was to inject the type as a magic attribute.
But this turned out to make the implementation brittle, asymmetric
and either quite demanding, or inefficient.
The only sane approach would be to introduce a third collection,
the metadata attributes. Then it would be possible to handle these
automatically, but expose them through the iterator.
In the end I decided against it, just the type attribute
allone does not justify that effort. So now the type is an
special magic field and kept apart from any object data.
this solves the problem how to deal with value access
- for the simple default (string) implementation,
we use a 'key = val' syntax and thus have to split strings,
which means we need to return contents by value
- for the actual relevant use case we have GenNode entries,
which may recursively hold further Records. For dealing
with diff messages over this data struture, its a good
idea to allow for const& value access (otherwise we'd
end up copying large subtrees for trivial operaions)
OMG, what was all this about?
OK... this cant possibly work this way.
At least we need to trim after splitting the attributes.
But this is not enough, we want the value, which implies
to make the type flexible (since we cant return a const& to
a substring extracted on-the-fly)
this was an half hearted attempt to satisfy CLang,
but GCC as keen as a razor insists on these inherited
functions not being accessible --
seems like the time is over, when GCC used to be forgiving
and CLang briliantly precise...
So the conclusion of this "round trip" is: whenever GCC
also starts whining about shadowed overloaded virtual functions,
we'll just switch to "-Wno-overloaded-virtual" and be done with
that pointless discussion.
Since C++11, we have the Java style override specifier,
which does a way better job at spotting signature mismatches
Note: not fixing all relevant warnings.
Especially, the "-Woverloaded-virtual" of Clang defeats the whole purpose
of generated generic interfaces. For example, our Variant type is instantiated
with a list of types the variant can hold. Through metaprogramming, this
instantiation generates also an embedded Visitor interface, which has
virtual 'handle(TY)' functions for all the types in question
The client now may implement, or even partially implement this Visitor,
to retrieve specific data out of given Variant instance with unknown conent.
To complain that some other virtual overload is now shaddowed is besides the point,
so we might consider to disable this warning altogether
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56402
The lambda definition captures the this pointer,
but the ctor of the lamda does not initialise this capture.
In our case, we're lucky, as we don't use the "this" pointer;
otherwise, we'd get a crash a runtime.
Fixed since GCC-4.7.3 --> it's *really* time to upgrade to Debian/Jessie
the object VTable is typically emitted when the compiler
encounters the first non-static non-inline function of
the class or a derived class.
Sometimes this happens within the wrong library and so
the compiler needs a nudge to emit those infrastructure functions.
But in most cases this works out of the box and need no further
magic incanctations, which might have a downside.
Especially because also a non-inline dtor does incur a call overhead,
whereas an inline dtor can be trivially elided.
after sleeping a night over this, it seems obvios
that we do not want to start the build proces "implicitly",
starting from a Record<GenNode>. Rather, we always want
the user to plant a dedicated Mutator object, which then
can remain noncopyable and is passed by reference through
the whole builder chain. Movin innards of *this object*
are moved away a the end of the chain does not pose much risk.
especially I've now decided how to handle const-ness:
We're open to all forms of const-ness, the actual usage decides.
const GenNode will only expose a const& to the data values
still TODO is the object builder notation for diff::Record
forwarding equality to the embedded EntryID
Basically, two GenNodes are equal when they have the same "identity"
Ironically, this is the usual twist with database entities
on a second thought, this "workaround" does not look so bad,
due to the C++11 feature to request the default implementation explicitly.
Maybe we'll never need a generic solution for these cases
I decided to allow for an 'unbound' reference to allow
default construction of elements involving record references.
I am aware of the implications, but I place the focus
on the value nature of GenNode elements; the RecordRef
was introduced only as a means to cary out diff comparisons
and similar computations.
basically this is the well known problem #587
Just it became more pressing with the Upgrade to Jessie and Boost 1.55
So I've pulled off the well known "Knuth trick" to spread the
input data more evenly within the hash domain.
And voilà: now we're able to use 100000 number suffixes without collision
- move the santitise operation up into EntryID's ctor
- turn the recast() operation into a real in-place cast
these changes should be transparent to the existing usages
of EntryID (within the asset framework), but allow for use
as attribute name holder in GenNode, since we're now able
to feed existing name/ID values directly into the ctor
of BareEntryID, without any spurious santitise operation.
this was introduced into namespace mobject and spread from there.
Since the habit is to use more specific typedefs like PClip,
it is preferrable to spell out the full namespace
using the struct-scheme.hpp and the requirements for
EntryID as a guideline. The goal is to move EntryID
over into the support lib, which means we need to get rid
of all direct proc::asset dependencies. Thus, these generic
ID functions shall form a baseline implementation, while
asset::Struct may provide the previously used implementation
through specialisation -- so the behaviour of EntryID will
not change for the structural assets, but we'll get a more
sane and readable default implementation for all other types.
before engaging into the implementation of lib::Record,
I prefer to conduct a round of planning, to get a clearer
view about the requirements we'll meet when extending
our existing list diff to tree structures
Initially, I considered to build an index table like
collection of ordered attributes. But since our actual
use case is Record<GenNode>, this was ruled out in favour
of just a vector<GenNode>, where the keys are embedded
right within the nameID-Field of GenNode.
A decisive factor was the observation, that this design
is basically forced to encode the attribute keys somehow
into the attribute values, because otherwise the whole
collection like initialisation and iteration would break
down. Thus, a fully generic implementation is not possible,
and a pseudo generic implementation just for the purpose of
writing unit tests would be overkill.
Basically this decision means that Record requires an
explicit specialisation to implement the attribute-key
binding for each value type to use.
Ouch!
Why does C++ lack the most basic everyday stuff?
It needn't be performant. It needn't support some fancy
higher order container. Just join the f***ing strings.
use Bosst?? -- OMG!! pulls in half the metra programming library
and tries to work on any concievable range like object. Just
somehow our Lumiera Forward Iterators aren't "range-like" enough
for boost's taste.
Thus let's code up that fucking for-loop ourselves, once and forever.
This is kind of the logic consequence, since we consider our
functional iterator concept still superior and will continue
to rely on it.
For some time now, I've considered to build a generic bridge
function, to use enable_if and metaprogramming to figure out
if some type is a "Lumiera Forward Iterator" automatically.
But since our concept is to some degree a contract regarding
semantics, which never can be captured by any kind of introspection,
such a bridge implementation would be rather heuristic and
bears the danger to trigger on types actually not intended
as iterator at all. So I consider such a solution as dangerous
and we'll settle with just supplying the necessary bridge
functions as free functions injected for ADL on a case by case base
this was spotted by a new GCC warning -Wunused-function
and I must admit, GCC is right here: an externally not visible
function in an anonymous namespace is not what I'd expect to be
picked up by ADL. It is rather weird that the metaprogramming
trait worked at all.
Note that the function is intentionally declared only, never defined.
We want a linker error in case boost::hash ever attempts to
use this 'deliberately ill-definded' catch-all.
I'd never imagine that this superficial draft will sit there
for 5+ years without me getting any chance to continue with that topic.
this is so saddening, so I turned off the warning :-/
In Lumiera, "Tracks" are not what you'd expect from
conventional video editing software. They are a mere
grouping devide, and are also used to implement the
"media bins" and tool palettes.
But having "folders" on the timeline would be likewise
confusing, as would be to have a "branch" or "tree".
To get out of that dilemma, we chose an understandable
but deliberately somewhat strange name: "Fork"
It was common understanding on the Mailinglist that we
should handle this renaming in a tuned-down and discrete
way: The UI will continue to show "Tracks" for a familiar
sight and "Bins" in the Asset section. But Lumiera developers
will be nudged to accomodate by renaming the entity in
source code accordingly
Cockoo hashing is a thrilling algorithm.
We investigated it during the time or our first draft
towards a confirugation system in 2008. This usage turned
up some problems -- not sure if based on the implementation
or the algorithm itself; at that time, we just switched
to the probabilistic splay tree. The whole configuration
system effort stalled afterwards; so the cuckoo implementation
remained in tree as a zombie.
This switches the Lumiera UI from GTK-2 to GTK-3
Unfortunately, this move breaks two crucial features, which have been
disabled for now: the display of video and our custom timeline widget.
Since both of these require some reworking, which in fact has already
started, we prefer to do the library and framework switch right away.
over time, a specific Lumiera code writing style has emerged.
The GUI, as it stood, used somewhat different conventions,
which now have been aligned to the common standard.
Basically we use GNU style, with some adjustments for OO-programming,
we prefer CamelCase, and write TypeNames uppercase, variableNames lowercase
it is a widely accepted rule to shape names with the usage site in mind.
Especially this means, that we use the singular form for all kinds
of collections and assortments.
Thus, the namespace should be called "widget" not "widgets",
because at usage site this becomes gui::widget::TimelineWidget
Likewise for "dialogs" and "pannels"
a long standing TODO to document the actual start-up sequence, which
is implemented this way since a long time now. There was an unwritten
section in the "Linking and Application Structure", which seems the
apropriate place for this kind of intricate techincal details.
Last week, Benny Lyons was here on visit in munich and he was pondering
the idea of an experimental secondary build system, as a way to learn
more about the source structure of Lumiera. This reminded me to fill
some missing parts of the documentation. Possibly this is also the
right moment to land the GTK-3 transition?
The actual trick to make it work is to use decltype on the function operator
http://stackoverflow.com/questions/7943525/is-it-possible-to-figure-out-the-parameter-type-and-return-type-of-a-lambda/7943765#7943765
In addition, we now pick up the functor by template type and
store it under that very type. For one, this cuts the size
of the generated class by a factor of two. And it gives the
compiler the ability to inline a closure as much as is possible,
especially when the created Binder / Mutator lives in the same
reference frame the closure taps into.
to carry out that rather obvious step, I was bound to consider
all the implications of choosing a given layout and handling pattern
for our external structure representation.
Finally, I settled upon the following decisions
- the value space represented within the DataCap is flat, not further structured
- the distinction between "attribute" and "nested object" is merely conceptual
and will be enforced solely by the diff detection / representation protocol
- basically, a nested subtree may appear as an attribute; the difference
between attributes and children lies solely in the way of access and referral:
by-name vs. positional
- it is pointless to save space for the representation of the discriminator ID
- but we can omit any further explicit type tag, because
- we do *not* support programming by switch-on-type, and thus
- we do *not* support full introspection, only a passive type-safety check
- this is *not* a limitation, since we acknowledge that GenNode is a *Monad*
- and the partial function needed within any flatMap implementation
maps naturally onto our Variant-Visitor; thus
- the DataCap can basically just *be* a Variant
- and GenNode has just to supply the neccessary shaffolding
to turn that into a full fledged Monad implementation, including
direct construction by wrapping a value and flatMap with tree walk
All relevant uses will rely on the more strict access policy
implemented with the new util::AccessCasted. Along the same line
of thinking, I've removed the "second try" convenience conversion
from the typed get-Function of OpaqueHolder. Such an unbounded
"convert it somehow" approach is almost never a good idea. Either,
one knows by design the precise type to expect, or alternatively
should rely on the base interface solely.
...with the sole exception of the usage in WrapperPointer,
which in itself looks obsolete to me; we should better re-think
the way we handle "wrapped" objects for the BuilderTools, once
we actually start implementing the Builder
Ticket #450
Note: the new Variant implementation is a re-write from scratch
and does not rely on util::AccessCasted any more. Anyway, both
are now thoroughly covered by unit test
NOTE: this was a one-time verification. Unfortunately there is no way
to verify a failing compilation automatically from a unit-test.
Thus we need to comment out these invalid cases, leaving them
here just for later referral. Need to check those manually
for new compilers to be sure!
this overload will be picked only if none of the more specific
overloads is applicable. Instantiating this overload will then
trigger a static assertion failure. This way we sort out
impossible or dangerous combinations at compile time already.
I found no simple way to include the actual type parameters in
the generated error message (string concatenation at compiletime)
The throw-statement is only there to prevent a warning due
to missing return statement.
...since I consider that a comparatively safe convenience feature.
Of course we *do perform* a NULL check and throw an exception.
So now the actual casting or conversion functions are designed
to work always on the same level of references or pointers,
which means we can just use the standard conversions of the
language. This has the nice effect of ruling out dangerous
combinations (like taking a L-ref from a R-ref) automatically
TODO: might break some unit-tests...
Explanation: our wrapper around boost::format has special
built-in support for custom operator string(). Any type,
which is neiter standard, or printable through such a
custom string conversion, is represented as a type-string.
For this fallback case, we now use our recently added
demangling call (which actually relies on a rather obscure
but standard compiler API)
still passes compilation, but not actually tested.
The visitor-style accees needs to be implemented, and the
whole virtual copy support mechanism extracted into a separate
header and covered by unit test
now the solution with the copy policy class is in place,
I prefer to return to the more verbose yet clearer notion
of distinct constructors for each case on the outer and
the inner capsule likewise.
The idea with the separate builder class would be significant
only if this class would also provide the copy support. This
turns out to be difficult, due to the access restrictions
and the necessary passing of type parameters.
turns out to be quite a tough challenge....
since obviously we want to support usage of types with
partially disabled copy/assignment operations within Variant.
As long as the corresponding operations on the container aren't
invoked, we expect those types to be usable just fine.
The problem arises at the interaction with type erasure;
to support corret copy / assignement in such a situation, we need
virtual copy / assignment operators. And, since these are to be installed
into a VTable, the templated functions will be instantiated allways,
which might cause invocation of inhibited copy / assignement functions
and thus compilation failure, in spite of never actually invoking such
an illegal operation.
The drafted solution is to mix in a specifically configured copy support policy,
which at least raises a runtime error, instead of invoking the incriminating operation(s)
finally got all those copy / assgnment flavours straight.
Still unsolved: unable to instantiate the Variant template
for a type with private assignment operator (like e.g. Time )
The problem is our virtual assignement operator, which forces
instantiation of the implementation (for the VTable), even if
the actual assignment is never invoked.
this was an immature first desgin attempt; we need a lightweight
Variant (typesafe union) implementation, so now is the time for
a second attempt. The existing Variant is used only once, and this
usage as such is in a questionable context, likely to be reworked
when we actually start coding up the builder. So I'll just move
it away and mark it @deprecated for the time being.
After some reconsideration, I decide to stick to the approach with the closures,
but to use a metaprotramming technique to build an inheritance chain.
While I can not decide on the real world impact of storing all those closures,
in theory this approach should enable the compiler to remove all of the
storage overhead. Since, when storing the result into an auto variable
right within scope (as demonstrated in the test), the compiler
sees the concrete type and might be able to boil down the actual
generated virtual function implementations, thereby inlining the
given closures.
Whereas, on the other hand, if we'd go the obvious conventional route
and place the closures into a Map allocated on the stack, I wouldn't
expect the compiler to do data flow analysis to prove this allocation
is not necessary and inline it away.
NOTE: there is now guarantee this inlining trick will ever work.
And, moreover, we don't know anything regarding the runtime effect.
The whole picture is way more involved as it might seem at first sight.
Even if we go the completely conventional route and require every
participating object to supply an implementation of some kind of
"Serializable" interface, we'll end up with a (hand written!)
implementation class for each participating setup, which takes
up space in the code segment of the executable. While the closure
based approach chosen here, consumes data segment (or heap) space
per instance for the functors (or function pointers) representing
the closures, plus code segment space for the closures, but the
latter with a way higher potential for inlining, since the closure
code and the generated virtual functions are necessarily emitted
within the same compilation unit and within a local (inline, not
publickly exposed) scope.
so yes, it is complicated, and inevitably involves three layers
of indirection. The alternative seems to bind the GUI direcly to
the Session interface -- is there a middle gound?
For the messages from GUI to Proc, we have our commands, based
on PlacementRef entities. But for feeding model updates to the
GUI, whatever I consider, I end up either with diff messages or
an synchronised access to Session attributes, which ties the
responsiveness of the GUI to the Builder operation.
- we use a GenNode element
- this holds a polymorphic value known as DataCap
- besides simple attribute values, this may hold collections of GenNode sub elements
- a special kind of GenNode collection, the Record, is used to represent objects
The purpose of this setup is to enable an external model representation
which is only loosely coupled to the interndal data representation
through the exchange of (tree)diff messages
previously this operation was named 'attach', which an be confused
with attching an object to this location. Indeed, the session interface
even offers such an attach function. By renaming the focus moving
operation into QueryFocus::shift(Scope), this ambiguity is resolved
This is the first step towards a generic backbone to connect
any GUI elements to the session within Proc-Layer.
It is based on a spefic understanding of Model-View-Controller,
which turns the Model-Controller interactions into messages.
sans the implementation of the index lookup table(s)
The algorithm is KISS, a variant of insertion sort, i.e.
worst time quadratic, but known to perform well on small data sets.
The mere generation of the diff description is O(n log n), since
we do not verify that we can "find" out of order elements. We leave
this to the consumer of the diff, which at this point has to scan
into the rest of the data sequence (leading to quadratic complexity)
finally....
The problem is that the C++ "dependent types" defeat the typical
DSL usage, where you define some helper function in a generic
language setup class and mix this language in as superclass.
This is, C++ requires us to refer explicitly to any dependent type,
since, due to possible template specialisations, the parser
can't know if a given symbol is a inherited type or a field.
As a solution, we place the token constructor functors into a
static struct "token", which allows to write e.g. token.insert(xyz)
As decided in beb57cde
this changeset switches our basic list diff language to work
in the style of an insertion sort. Rather than 'pushing back'
out-of-order elements, we scan and bring forward missing elements.
Later, when passing the original location of the elements
fetched this way, a 'skip' verb will help to clean up
possible leftowers, so implementation is possible
(and indeed acomplished) without shifting any other elements.
and this adds a twist: conceptually, we identify the token
with the abstract handler function it represents. But C++
does not allow us to compare member pointers to virtual functions,
for good reason: even two pointers with the "same offset" into
the VTable might end up referring to different implementations,
when bound to instances of different subclasses. This is what
polymorphism is all about.
At this point it seems reasonably, albeit a bit uggly, to use the
diagnostic ID as placeholder instead, and just compare these IDs
instead. We assume that in practice tokens will be defined through
the provided helper macro, which ensures unique identifiers.
basically just a function to pick up the container and element type automatically.
The actual implementation is delegated to the exisiting lib::iter_stl::IterSnapshot
Heureka! found out that the C++ standard library exposes a
cross vendor C++ ABI, which amongst others allows to show
object code names and type-IDs in the language-level, human
readable unmangeld form.
Of course, actual application code should not rely on such a
internal representation, yet it is of tremendous help when
writing and debugging unit tests.
Signed-off-by: Ichthyostega <prg@ichthyostega.de>
Actually I arried at the conclusion, that the *receiving* of
a diff representation is actually a typical double-dispatch situation.
This leads to the attempt to come up with a specialised visitor
as standard pattern to handle and apply a diff. Obviously,
we do not want the classical GoF-Visitor, but (yes, we had
that discussion allready) -- well in terms of runtime cost,
we have to deal with at least two indirections anyway;
so now I'm exploring the idea to implement one of these
indirections through a functor object, which at the same time
acts as "Tag" in the diff representation language (instead
of using an enum as tag)
Uniform sequence at start of source files
- copyright claim
- license
- file comment
- header guard
- lumiera includes
- library / system includes
Lumiera uses Brittish spelling. Add an according note to the styleguide.
initial considerations; there is a concurrency problem, since
all of session handling within Proc is deliberately not threadsafe.
Thus the decision is to make this the gui::model::SessionFacade's responsibility
The actual problem is not resolved; the pluginloader
should detect the duplicate and not add the handle
to the database initially. Or it should add it
as "duplicate" or "alternate implementation"
Which probably means we need to coder some additional
corner cases. But certainly not now, we have other
more important stuff to do first... we've already
lost the battle against Duke Nukem Forever :-P
