Ichthyostega
4a7e1eeb36
Why is our specialisation of `std::get` not picked up by the compiler? * it must somehow be related to the fact that `std::tuple` itself is a base class of lib::HeteroData * if we remove this inheritance relation, our specialisation is used by the compiler and works as intended * however, this strange behaviour can not be reproduced in a simple synthetic setup It must be some further subtlety which marks the tuple case as preferrable
78 lines
1.6 KiB
C++
78 lines
1.6 KiB
C++
/* try.cpp - to try out and experiment with new features....
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* scons will create the binary bin/try
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*/
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// 12/24 - investigate overload resolution on a templated function similar to std::get
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// 11/24 - how to define a bare object location comparison predicate
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// 11/23 - prototype for grouping from iterator
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/** @file try.cpp
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* Find out about the conditions when an overload of a function template is picked.
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* This is an investigation regarding the proper way to overload std::get
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* especially when the base class of the custom type itself is a tuple.
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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/test/diagnostic-output.hpp"
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#include "lib/util.hpp"
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#include <utility>
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#include <string>
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#include <tuple>
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using lib::test::showType;
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template<typename...TS>
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string
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showTypes()
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{
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return "<" + ((showType<TS>()+",") + ... + ">");
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}
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using std::tuple;
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struct B { };
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struct D1 : B { };
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struct D2 : D1 { };
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string getty (B&) { return "getty-B&"; }
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string getty (D1&&){ return "getty-D1&&"; }
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string getty (D1&) { return "getty-D1&"; }
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template<class...TS>
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string getty (tuple<TS...>&) { return "getty-tuple& "+showTypes<TS...>(); }
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template<class...TS>
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struct F : tuple<TS...> { };
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template<class...TS>
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struct FD1 : F<TS...> {};
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template<class...TS>
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struct FD2 : FD1<TS...> {};
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template<class...TS>
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string getty (FD1<TS...>&) { return "getty-FD1& "+showTypes<TS...>(); }
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int
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main (int, char**)
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{
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D2 d2;
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SHOW_EXPR(getty(d2));
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FD2<int, char**> fd2;
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SHOW_EXPR(getty(fd2));
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cout << "\n.gulp.\n";
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return 0;
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}
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