Ichthyostega
97727a6283
using function calls here, but in the end, what we want is to invoke some ctor with part of the provided argument sequence
140 lines
3.9 KiB
C++
140 lines
3.9 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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// 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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/** @file try.cpp
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** Metaprogramming: manipulations on variadic template argument packs.
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** Investigation how to transform a parameter pack such as to forward a fixed chunk
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** to one sub-ctor and delegate the rest to a tail recursive call.
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**
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** This investigation was spurred by an attempt to create an inline storage layout
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** with possible heap-based extension. Being able to build such an object layout
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** would enable several possibly interesting optimisations when most usage scenarios
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** of a class will only use a small element count, while some usages still require
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** an essentially unlimited open number of elements.
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**
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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/format-util.hpp"
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//#include "lib/meta/function.hpp"
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#include "lib/meta/tuple-helper.hpp"
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#include <functional>
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#include <utility>
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#include <string>
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using lib::meta::_Fun;
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using std::function;
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using std::forward;
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using std::move;
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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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void
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fun1 (int i, int j, int k)
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{
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cout << "FUN-1: "<<i<<" "<<j<<" "<<k<<" " <<endl;
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}
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void
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fun2 (int const& i, int const& j, int const& k)
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{
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cout << "FUN-2: "<<i<<" "<<j<<" "<<k<<" " <<endl;
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}
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template<size_t...idx>
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struct Idx
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{ };
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template<typename...ARGS>
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struct IdxSeq
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{
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template<size_t>
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struct First
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{
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};
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};
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template<size_t...idx>
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struct Pick
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{
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template<typename...ARGS>
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Pick (ARGS... args)
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{ }
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};
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template<size_t...idx, typename...ARGS>
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void
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dispatch (Idx<idx...>, ARGS...args)
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{
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fun1 (Pick<idx>{args...} ...);
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}
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template<typename...ARGS>
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void
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dispatch (ARGS...args)
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{
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using First = typename IdxSeq<ARGS...>::template First<3>;
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dispatch_ (First{}, args...);
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}
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int
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main (int, char**)
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{
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fun1 (1,2,3);
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fun2 (4,5,6);
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// dispatch (2,3,4,5,6,7,8);
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cout << "\n.gulp.\n";
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return 0;
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}
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