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Research: build "anything function-like" trait

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...with the sole exception that such a trait can not detect
a templated or overloaded function call operator
This commit is contained in:
Fischlurch 2017-11-24 02:16:57 +01:00
parent 2533565f83
commit 8bdd9e7d66
2 changed files with 83 additions and 24 deletions
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103
research/try.cpp
View file

@ -78,11 +78,11 @@ namespace meta{
using Sig = Ret(ARGS...); using Sig = Ret(ARGS...);
}; };
template<typename FUN, typename...ARGS> template<typename FUN>
class can_Invoke class can_Invoke
{ {
template<typename FF, template<typename FF,
typename SEL = decltype(std::declval<FF>() (std::declval<ARGS>()...))> typename SEL = decltype(&FF::operator())>
struct Probe struct Probe
{ }; { };
@ -96,28 +96,62 @@ namespace meta{
}; };
template<class FUN, typename TYPES, typename SEL =void> template<typename FUN, typename SEL =void>
struct ProbeFunctionArgument struct _FunT
{ : std::false_type
static_assert(not sizeof(FUN), "Tilt");
};
template<class FUN, typename T, typename TYPES>
struct ProbeFunctionArgument<FUN, Node<T,TYPES>, enable_if<can_Invoke<FUN,T>> >
: ProbeFunctionInvocation<FUN,T>
{ }; { };
template<class FUN, typename T, typename TYPES> template<typename FUN>
struct ProbeFunctionArgument<FUN, Node<T,TYPES>, disable_if<can_Invoke<FUN,T>> > struct _FunT<FUN, enable_if<can_Invoke<FUN>> >
: ProbeFunctionArgument<FUN, TYPES> : _FunT<decltype(&FUN::operator())>
{ };
/** Specialisation for a bare function signature */
template<typename RET, typename...ARGS>
struct _FunT<RET(ARGS...)>
: std::true_type
{ {
using Ret = RET;
using Args = Types<ARGS...>;
using Sig = RET(ARGS...);
}; };
/** Specialisation for using a function pointer */
template<typename SIG>
struct _FunT<SIG*>
: _FunT<SIG>
{ };
/** Specialisation when using a function reference */
template<typename SIG>
struct _FunT<SIG&>
: _FunT<SIG>
{ };
/** Specialisation for passing a rvalue reference */
template<typename SIG>
struct _FunT<SIG&&>
: _FunT<SIG>
{ };
/** Specialisation to deal with member pointer to function */
template<class C, typename RET, typename...ARGS>
struct _FunT<RET (C::*) (ARGS...)>
: _FunT<RET(ARGS...)>
{ };
/** Specialisation to handle member pointer to const function;
* indirectly this specialisation also handles lambdas,
* as redirected by the main template (via `decltype`) */
template<class C, typename RET, typename...ARGS>
struct _FunT<RET (C::*) (ARGS...) const>
: _FunT<RET(ARGS...)>
{ };
}} }}
using lib::meta::Types; using lib::meta::Types;
using lib::meta::can_Invoke; using lib::meta::_FunT;
using lib::meta::ProbeFunctionArgument; using lib::meta::enable_if;
#define SHOW_TYPE(_TY_) \ #define SHOW_TYPE(_TY_) \
@ -126,6 +160,26 @@ using lib::meta::ProbeFunctionArgument;
cout << "Probe " << STRINGIFY(_XX_) << " ? = " << _XX_ <<endl; cout << "Probe " << STRINGIFY(_XX_) << " ? = " << _XX_ <<endl;
long
funny(int i)
{
return i+1;
}
template<typename FUN, typename SEL =void>
struct FunTrait
{
using XXX = decltype(std::declval<FUN>() (0));
static string doIt() { return "Uh OH:" + lib::meta::typeStr<XXX>(); }
};
template<typename FUN>
struct FunTrait<FUN, enable_if<_FunT<FUN>> >
{
static string doIt() { return "Yeah FUN:" + lib::meta::typeStr<typename _FunT<FUN>::Sig>(); }
};
int int
main (int, char**) main (int, char**)
@ -136,13 +190,18 @@ main (int, char**)
SHOW_TYPE (decltype(lamb1)); SHOW_TYPE (decltype(lamb1));
SHOW_TYPE (decltype(lamb2)); SHOW_TYPE (decltype(lamb2));
SHOW_EXPR ((can_Invoke<decltype(lamb1), string>::value)); SHOW_EXPR ((_FunT<decltype(lamb1)>::value));
SHOW_EXPR ((can_Invoke<decltype(lamb2), int>::value )); SHOW_EXPR ((_FunT<decltype(lamb2)>::value));
SHOW_EXPR ((_FunT<decltype(funny)>::value));
SHOW_EXPR ((_FunT<decltype(&funny)>::value));
using InferredSIG = typename ProbeFunctionArgument<decltype(lamb1), typename Types<string,long,int>::List>::Sig; auto funky = function<double(float)> (lamb2);
//NOTE does not work with the generic lamb2, because instantiating lab2(string) would be a *compile* error, not a substitution failure SHOW_EXPR ((_FunT<decltype(funky)>::value));
SHOW_TYPE (InferredSIG); cout << FunTrait<decltype(lamb1)>::doIt() <<endl;
cout << FunTrait<decltype(lamb2)>::doIt() <<endl;
cout << FunTrait<decltype(funny)>::doIt() <<endl;
cout << FunTrait<decltype(funky)>::doIt() <<endl;
cout << "\n.gulp.\n"; cout << "\n.gulp.\n";

4
wiki/thinkPad.ichthyo.mm
View file

@ -5234,8 +5234,8 @@
</html> </html>
</richcontent> </richcontent>
</node> </node>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1511455607914" HGAP="56" ID="ID_1866082603" MODIFIED="1511455626668" TEXT="Untersuchung" VSHIFT="39"> <node CREATED="1511455607914" HGAP="56" ID="ID_1866082603" MODIFIED="1511486111045" TEXT="Untersuchung" VSHIFT="39">
<icon BUILTIN="pencil"/> <icon BUILTIN="button_cancel"/>
<node CREATED="1511455644829" ID="ID_1545300823" MODIFIED="1511455655796" TEXT="ist generisches Labmda detektierbar?"> <node CREATED="1511455644829" ID="ID_1545300823" MODIFIED="1511455655796" TEXT="ist generisches Labmda detektierbar?">
<icon BUILTIN="help"/> <icon BUILTIN="help"/>
<node CREATED="1511482195487" ID="ID_954120351" MODIFIED="1511482198474" TEXT="jein"/> <node CREATED="1511482195487" ID="ID_954120351" MODIFIED="1511482198474" TEXT="jein"/>