Yet another chainsaw massacre.
One of the most obnoxious annoyances with C++ metaprogramming
is the need to insert `typename` and `template` qualifiers into
most definitions, to help the compiler to cope with the syntax,
which is not context-free.
The recent standards adds several clarifications, so that most
of these qualifiers are redundant now, at least at places where
it is unambiguously clear that only a type can be given.
GCC already supports most of these relaxing rules
(Clang unfortunately lags way behind with support of newer language features...)
...which should ''basically work,'' since `std::array` is ''»tuple-like«'' —
BUT unfortunately it has a quite distinct template signature which does not fit
into the generic scheme of a product type.
Obviously we'd need a partial specialisation, but even re-implementing this
turns out to be damn hard, because there is no way to generate a builder method
with a suitable explicit type signature directly, because such a builder would
need to accept precisely N arguments of same type. This leads to a different
solution approach: we can introduce an ''adapter type'', which will be layered
on top of `std::array` and just expose the proper type signature so that the
existing Implementation can handle the array, relying on the tuple-protocol.
__Note__: this changeset adds a convenient pretty-printer for `std::array`,
based on the same forward-declaration trick employed recently for `lib::Several`.
You need to include 'lib/format-util.hpp' to actually use it.
Some additional tests to challenge the parser, which seems to work well.
Without extended analysis into the usage of those node specifications,
it is pointless to expand further on its capabilities. For now, it is
sufficient to have a foundation for hash-computation in place.
__Note__: found a nifty way to give lib::Several an easy toString rendering,
without cranking up the header inclusion load.
Basically I am sick of writing for-loops in those cases
where the actual iteration is based on one or several data sources,
and I just need some damn index counter. Nothing against for-loops
in general — they have their valid uses — sometimes a for-loop is KISS
But in these typical cases, an iterator-based solution would be a
one-liner, when also exploiting the structured bindings of C++17
''I must admit that I want this for a loooooong time —''
...but always got intimidated again when thinking through the fine points.
Basically it „should be dead simple“ — as they say
Well — — it ''is'' simple, after getting the nasty aspects of tuple binding
and reference data types out of the way. Yesterday, while writing those
`TestFrame` test cases (which are again an example where you want to iterate
over two word sequences simultaneously and just compare them), I noticed that
last year I learned about the `std::apply`-to-fold-expression trick, and
that this solution pattern could be adapted to construct a tuple directly,
thereby circumventing most of the problems related to ''perfect forwarding''
So now we have a new util function `mapEach` (defined in `tuple-helper.hpp`)
and I have learned how to make this application completely generic.
As a second step, I implemented a proof-of-concept in `IterZip_test`,
which indeed was not really challenging, because the `IterExplorer`
is so very sophisticated by now and handles most cases with transparent
type-driven adaptors. A lot of work went into `IterExplorer` over the years,
and this pays off now.
The solution works as follows:
* apply the `lib::explore()` constructor function to the varargs
* package the resulting `IterExplorer` instantiations into a tuple
* build a »state core« implementation which just lifts out the three
iterator primitives onto this ''product type'' (i.e. the tuple)
* wrap it in yet another `IterExplorer`
* add a transformer function on top to extract a value-tuple for each ''yield'
As expected, works out-of-the-box, with all conceivable variants and wild
mixes of iterators, const, pointers, references, you name it....
PS: I changed the rendering of unsigned types in diagnostic output
to use the short notation, e.g. `uint` instead of `unsigned int`.
This dramatically improves the legibility of verification strings.
* Lumiera source code always was copyrighted by individual contributors
* there is no entity "Lumiera.org" which holds any copyrights
* Lumiera source code is provided under the GPL Version 2+
== Explanations ==
Lumiera as a whole is distributed under Copyleft, GNU General Public License Version 2 or above.
For this to become legally effective, the ''File COPYING in the root directory is sufficient.''
The licensing header in each file is not strictly necessary, yet considered good practice;
attaching a licence notice increases the likeliness that this information is retained
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situation, but rather creates a derivative work, which is likewise covered by the GPL!
The most relevant information in the file header is the notice regarding the
time of the first individual copyright claim. By virtue of this initial copyright,
the first author is entitled to choose the terms of licensing. All further
modifications are permitted and covered by the License. The specific wording
or format of the copyright header is not legally relevant, as long as the
intention to publish under the GPL remains clear. The extended wording was
based on a recommendation by the FSF. It can be shortened, because the full terms
of the license are provided alongside the distribution, in the file COPYING.
showing the Node-symbol and a reduced rendering of
either the predecessor or a collection of source nodes.
For this we need functionality to traverse the node graph depth-first
and collect all leaf nodes (which are the source nodes without predecessor);
such can be implemented with the help of the expandAll() functionality
of `lib::IterExplorer`. In addition we need to collect, sort and deduplicate
all the source-node specs; since this is a common requirement, a new
convenience builder was added to `lib::IterExplorer`
- it is not directly possible to provide a variadic join(args...),
due to overload resolution ambiguities
- as a remedy, simplify the invocation of stringify() for the typical cases,
and provide some frequently used shortcuts
This is a subtle and far reaching fix, which hopefully removes
a roadblock regarding a Dispatcher pipeline: Our type rebinding
template used to pick up nested type definitions, especially
'value_type' and 'reference' from iterators and containers,
took an overly simplistic approach, which was then fixed
at various places driven by individual problems.
Now:
- value_type is conceptually the "thing" exposed by the iterator
- and pointers are treated as simple values, and no longer linked
to their pointee type; rather we handle the twist regarding
STL const_iterator direcly (it defines a non const value_type,
which is sensible from the STL point of view, but breaks our
generic iterator wrapping mechanism)
surprise: the standard for-Loop causes a copy of the iterator.
From a logical POV this is correct, since the iterator is named,
it can not just be moved into the loop construct and be consumed.
Thus: write a plain old-fashioned for loop and consume the damn thing.
So the top-level call into util::join(&&) decides, if we copy or consume
As it turned out, we had two bugs luring in the code base,
with the happy result of one cancelling out the adverse effects of the other
:-D
- a mistake in the invocation of the Itertools (transform, filter,...)
caused them to move and consume any input passed by forwarding, instead
of consuming only the RValue references.
- but util::join did an extraneous copy on its data source, meaning that
in all relevant cases where a *copy* got passed into the Itertools,
only that spurious temporary was consumed by Bug #1.
(Note that most usages of Itertools rely on RValues anyway, since the whole
point of Itertools is to write concise in-line transformation pipelines...)
*** Added additional testcode to prove util::stringify() behaves correct
now in all cases.
this becomes more relevant now, since the actual MutationMessage iterators
are implemented in terms of a shared_ptr to IterSource. Thus, when building
processing pipelines, we most definitively want to move that smart-ptr into
the destination, since this avoids touching the shared count and thus avoids
generating unnecessary memory barriers.
...also for the existing variant, which packages an
arbitrary number of arguments in stringified form
into a given container type. Moreover, the new
form of stringify allows to write util::join
in a clearer way, eliminating the lambda.
...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....
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
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....
- 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
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
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 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.
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.
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)
