137 lines
4.9 KiB
C++
137 lines
4.9 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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/** @file try.cpp
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** Metaprogramming: how to unload the contents of a runtime typed variant sequence
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** into ctor arguments of a (compile time typed) tuple. This involves two problems
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** - how to combine iteration, compile-time indexing and run-time access.
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** - how to overcome the runtime-to-compiletime barrier, using a pre-generated
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** double-dispatch (visitor).
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**
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** The concrete problem prompting this research is the necessity to receive
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** a command invocation parameter tuple from a Record<GenNode>
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**
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*/
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typedef unsigned int uint;
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#include "lib/symbol.hpp"
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#include "lib/time/timevalue.hpp"
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#include "lib/meta/tuple-record-init.hpp"
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#include "lib/format-cout.hpp"
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#include "lib/format-util.hpp"
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#include <boost/noncopyable.hpp>
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#include <string>
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using lib::Literal;
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using lib::Variant;
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using lib::idi::EntryID;
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using lib::diff::Rec;
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using lib::diff::MakeRec;
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using lib::diff::GenNode;
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using lib::meta::Types;
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using lib::meta::Tuple;
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using lib::meta::buildTuple;
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using lib::time::TimeVar;
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using lib::time::Time;
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using std::string;
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using std::tuple;
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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 EVAL_PREDICATE(_PRED_) \
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cout << STRINGIFY(_PRED_) << "\t : " << _PRED_ <<endl;
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void
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verifyConversions()
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{
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using lib::meta::GenNodeAccessor;
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using std::is_arithmetic;
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using std::is_floating_point;
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using lib::meta::is_nonFloat;
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using lib::hash::LuidH;
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EVAL_PREDICATE(is_arithmetic<int> ::value)
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EVAL_PREDICATE(is_arithmetic<size_t> ::value)
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EVAL_PREDICATE(is_floating_point<size_t>::value)
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EVAL_PREDICATE(is_nonFloat<size_t> ::value)
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EVAL_PREDICATE(GenNodeAccessor<int> ::allow_Conversion<size_t> ::value)
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EVAL_PREDICATE(GenNodeAccessor<int64_t>::allow_Conversion<long int>::value)
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EVAL_PREDICATE(GenNodeAccessor<double>::allow_Conversion<int64_t>::value)
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EVAL_PREDICATE(GenNodeAccessor<LuidH>::allow_Conversion<int64_t> ::value)
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EVAL_PREDICATE(GenNodeAccessor<LuidH>::allow_Conversion<int16_t> ::value)
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EVAL_PREDICATE(GenNodeAccessor<LuidH>::allow_Conversion<uint16_t>::value)
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EVAL_PREDICATE(GenNodeAccessor<LuidH> ::allow_Conversion<LuidH> ::value)
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EVAL_PREDICATE(GenNodeAccessor<int64_t> ::allow_Conversion<LuidH>::value)
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EVAL_PREDICATE(GenNodeAccessor<uint64_t>::allow_Conversion<LuidH>::value)
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EVAL_PREDICATE(GenNodeAccessor<uint32_t>::allow_Conversion<LuidH>::value)
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EVAL_PREDICATE(GenNodeAccessor<int32_t> ::allow_Conversion<LuidH>::value)
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cout <<endl<<endl;
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}
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int
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main (int, char**)
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{
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verifyConversions();
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using NiceTypes = Types<string, int>;
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using UgglyTypes = Types<EntryID<long>, string, int, int64_t, double, TimeVar>;
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Rec args = MakeRec().scope("lalü", 42);
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Rec urgs = MakeRec().scope("lalü", "lala", 12, 34, 5.6, Time(7,8,9));
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cout << args <<endl;
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cout << urgs <<endl;
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cout << buildTuple<NiceTypes> (args) <<endl;
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cout << buildTuple<UgglyTypes> (urgs) <<endl;
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cout << "\n.gulp.\n";
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return 0;
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}
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