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Add default dispatch handling for generic case of 'const rjp::value&'. Will cause compilation error if return type is not void

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This commit is contained in:
rexy712 2020-03-27 21:28:05 -07:00
parent 4bf41e8b42
commit 06cfc1d0b6
2 changed files with 32 additions and 1 deletions
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29
rjp++/include/dispatch.hpp
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@ -4,9 +4,17 @@
#include "rjp_internal.hpp" #include "rjp_internal.hpp"
#include <type_traits> //is_same, true_type, false_type #include <type_traits> //is_same, true_type, false_type
#include <utility> //forward #include <utility> //forward
#include <exception>
namespace rjp{ namespace rjp{
class missing_dispatch_handler : public std::exception
{
public:
const char* what(void)const noexcept override{
return "Argument not handled in rjp::dispatch";
}
};
namespace detail{ namespace detail{
template<RJP_data_type T> template<RJP_data_type T>
struct to_value_type; struct to_value_type;
@ -81,6 +89,23 @@ namespace rjp{
struct has_next_data_type{ struct has_next_data_type{
static constexpr bool value = has_next_data_type_helper<T>::value; static constexpr bool value = has_next_data_type_helper<T>::value;
}; };
template<class T, class Param>
struct has_operator_for{
template<class U, class = decltype(std::declval<U>()(std::declval<Param>()))>
static std::true_type check(U*);
static std::false_type check(...);
static constexpr bool value = std::is_same<std::true_type,decltype(check((void*)0))>::value;
};
template<class Param, class T, class... Ts>
struct has_operator_for_any{
static constexpr bool value = has_operator_for<T, Param>::value || has_operator_for_any<Param,Ts...>::value;
};
template<class Param, class T>
struct has_operator_for_any<Param,T>{
static constexpr bool value = has_operator_for<T,Param>::value;
};
template<class Func, class Val, RJP_data_type T> template<class Func, class Val, RJP_data_type T>
decltype(auto) dispatch_helper(Func&& fun, Val&& v){ decltype(auto) dispatch_helper(Func&& fun, Val&& v){
if(v.type() == T){ if(v.type() == T){
@ -89,6 +114,7 @@ namespace rjp{
if constexpr(detail::has_next_data_type<T>::value){ if constexpr(detail::has_next_data_type<T>::value){
return dispatch_helper<Func,Val,detail::next_data_type<T>::value>(std::forward<Func>(fun), std::forward<Val>(v)); return dispatch_helper<Func,Val,detail::next_data_type<T>::value>(std::forward<Func>(fun), std::forward<Val>(v));
} }
throw missing_dispatch_handler{}; //deals with -Wreturn-type warnings
} }
} }
template<class Func, class Val> template<class Func, class Val>
@ -99,6 +125,9 @@ namespace rjp{
struct dispatcher : public Ts... struct dispatcher : public Ts...
{ {
using Ts::operator()...; using Ts::operator()...;
template<typename std::enable_if<!detail::has_operator_for_any<const value&,Ts...>::value,void>::type* = nullptr>
decltype(auto) operator()(const value&)const{}
}; };
template<class... Ts> template<class... Ts>

4
rjp++/tests/dispatch.cpp
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@ -29,20 +29,22 @@ rjp::array initialize_array(int num){
int main(){ int main(){
srand(time(0)); srand(time(0));
int retval = 0;
rjp::array root = initialize_array(NUM_ELEMENTS); rjp::array root = initialize_array(NUM_ELEMENTS);
for(auto&& val : root){ for(auto&& val : root){
RJP_data_type d; RJP_data_type d;
rjp::dispatch(rjp::dispatcher{ rjp::dispatch(rjp::dispatcher{
[&d](const rjp::value&){assert(false);},
[&d](const rjp::integer&){d = rjp_json_integer;}, [&d](const rjp::integer&){d = rjp_json_integer;},
[&d](const rjp::boolean&){d = rjp_json_boolean;}, [&d](const rjp::boolean&){d = rjp_json_boolean;},
[&d](const rjp::array&){d = rjp_json_array;}, [&d](const rjp::array&){d = rjp_json_array;},
[&d](const rjp::object&){d = rjp_json_object;}, [&d](const rjp::object&){d = rjp_json_object;},
}, val); }, val);
if(d != val.type()){ if(d != val.type()){
++retval;
printf("Dispatch error\n"); printf("Dispatch error\n");
} }
} }
return retval;
} }