Ichthyostega
ff6234829a
Basically we want to create ElementBoxWidgets according to a preconfigured layout scheme, yet we'll need to pass some additional qualifiers and optional features, and these need to be checked and used in accordance with the chosen flavour... Investigating a possible solution based on additional ctor parameters, which are given as "algebraic terms", and actually wrap a functor to manipulate a builder configuration record
144 lines
4.7 KiB
C++
144 lines
4.7 KiB
C++
/* try.cpp - for trying out some language features....
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* scons will create the binary bin/try
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*
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*/
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// 8/07 - how to control NOBUG??
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// execute with NOBUG_LOG='ttt:TRACE' bin/try
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// 1/08 - working out a static initialisation problem for Visitor (Tag creation)
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// 1/08 - check 64bit longs
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// 4/08 - comparison operators on shared_ptr<Asset>
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// 4/08 - conversions on the value_type used for boost::any
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// 5/08 - how to guard a downcasting access, so it is compiled in only if the involved types are convertible
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// 7/08 - combining partial specialisation and subclasses
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// 10/8 - abusing the STL containers to hold noncopyable values
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// 6/09 - investigating how to build a mixin template providing an operator bool()
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// 12/9 - tracking down a strange "warning: type qualifiers ignored on function return type"
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// 1/10 - can we determine at compile time the presence of a certain function (for duck-typing)?
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// 4/10 - pretty printing STL containers with python enabled GDB?
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// 1/11 - exploring numeric limits
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// 1/11 - integer floor and wrap operation(s)
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// 1/11 - how to fetch the path of the own executable -- at least under Linux?
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// 10/11 - simple demo using a pointer and a struct
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// 11/11 - using the boost random number generator(s)
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// 12/11 - how to detect if string conversion is possible?
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// 1/12 - is partial application of member functions possible?
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// 5/14 - c++11 transition: detect empty function object
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// 7/14 - c++11 transition: std hash function vs. boost hash
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// 9/14 - variadic templates and perfect forwarding
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// 11/14 - pointer to member functions and name mangling
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// 8/15 - Segfault when loading into GDB (on Debian/Jessie 64bit
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// 8/15 - generalising the Variant::Visitor
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// 1/16 - generic to-string conversion for ostream
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// 1/16 - build tuple from runtime-typed variant container
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// 3/17 - generic function signature traits, including support for Lambdas
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// 9/17 - manipulate variadic templates to treat varargs in several chunks
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// 11/17 - metaprogramming to detect the presence of extension points
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// 11/17 - detect generic lambda
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// 12/17 - investigate SFINAE failure. Reason was indirect use while in template instantiation
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// 03/18 - Dependency Injection / Singleton initialisation / double checked locking
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// 04/18 - investigate construction of static template members
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// 08/18 - Segfault when compiling some regular expressions for EventLog search
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// 10/18 - investigate insidious reinterpret cast
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// 12/18 - investigate the trinomial random number algorithm from the C standard lib
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// 04/19 - forwarding tuple element(s) to function invocation
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// 06/19 - use a statefull counting filter in a treeExplorer pipeline
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// 03/20 - investigate type deduction bug with PtrDerefIter
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// 01/21 - look for ways to detect the presence of an (possibly inherited) getID() function
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// 08/22 - techniques to supply additional feature selectors to a constructor call
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/** @file try.cpp
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* Investigate techniques to supply additional descriptive ctor arguments in a type safe way.
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*/
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typedef unsigned int uint;
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#include "lib/format-cout.hpp"
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#include "lib/test/test-helper.hpp"
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#include "lib/util.hpp"
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//#include <utility>
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#include <functional>
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#include <string>
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using std::string;
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#define SHOW_TYPE(_TY_) \
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cout << "typeof( " << STRINGIFY(_TY_) << " )= " << lib::meta::typeStr<_TY_>() <<endl;
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#define SHOW_EXPR(_XX_) \
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cout << "Probe " << STRINGIFY(_XX_) << " ? = " << _XX_ <<endl;
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class Feat
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{
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string prop_{"∅"};
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using Manipulator = std::function<Feat(Feat)>;
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struct Qualifier
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: Manipulator
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{
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using Manipulator::Manipulator;
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};
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friend Qualifier bla();
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friend Qualifier blubb(string);
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public:
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operator string () const
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{
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return "Feat{"+prop_+"}";
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}
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Feat() = default;
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template<class... QS>
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Feat(Qualifier qual, QS... qs)
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: Feat{qual(Feat{qs...})}
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{ }
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};
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Feat::Qualifier
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bla()
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{
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return Feat::Qualifier{[](Feat feat)
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{
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feat.prop_ = "bla";
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return feat;
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}};
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}
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Feat::Qualifier
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blubb(string murks)
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{
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return Feat::Qualifier{[=](Feat feat)
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{
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feat.prop_ += ".blubb("+murks+")";
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return feat;
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}};
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}
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int
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main (int, char**)
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{
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Feat f0;
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SHOW_EXPR(f0);
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Feat f1(bla());
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SHOW_EXPR(f1);
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Feat f2(blubb("Ψ"));
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SHOW_EXPR(f2);
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Feat f3(bla(),blubb("↯")); // Note: evaluated from right to left, bla() overwrites prop
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SHOW_EXPR(f3);
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Feat f4(blubb("💡"), bla());
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SHOW_EXPR(f4);
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cout << "\n.gulp.\n";
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return 0;
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}
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