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Promise.cc
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Promise.cc
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#include <functional>
// template<class call, class...types>using _function = call(*)(types...); // tried to implement a namespace akin to std::function, but decided to stick to std::function in the long run
template<typename T,class TR=T> // the same embedded implementation of ECMA Promises in C++
class scope{
// template<class...types>using _TYPEC = _function<void, _function<void, T>, _function<void, TR>, types...>;
protected:private:
T resolveValue;
TR rejectValue;
bool c = false;
bool thenCheck = true, catchCheck = true;
// string state = "pending...";
T resolveBack(T arg){
return arg;
};
TR rejectBack(TR arg){
return arg;
};
scope(void); // cloak the constructor;
void _resolve(T args){
if(!c){
resolveValue = resolveBack(args);
c = true;
}
};
public:
void _reject(TR args){
if(!c){
rejectValue = rejectBack(args);
c = true;
}
};
scope(std::function<void(std::function<void(T)>, std::function<void(TR)>)> callback){
auto res = [this](T ar)->void{
this->_resolve(ar);
};
auto rej = [this](TR ar)->void{
this->_reject(ar);
};
try{
callback(res, rej);
}catch(TR err){
_reject(err);
}
}
scope(std::function<void(std::function<void(T)>)> callback){
auto res = [this](T ar)->void{ // bind design
this->_resolve(ar);
};
try{
callback(res);
}catch(TR err){
_reject(err);
}
}
static scope<T, TR> resolve(T);
static scope<T, TR> reject(TR);
scope<T, TR> then(std::function<void(T, TR)>);
scope<T, TR> then(std::function<void(T)>);
scope<T, TR>_catch(std::function<void(TR)>);
scope<T, TR> then(void);
T& await(void);
template<typename...types>
static scope<T, TR> async(std::function<T(types...)>, types...);
};
// specifications
template<class T, class TR>
scope<T, TR> scope<T, TR>::resolve(T item){
return scope<T, TR>([item](auto resolve){
resolve(item);
});
};
template<class T, class TR>
scope<T, TR> scope<T, TR>::reject(TR item){
return scope<T, TR>([item](std::function<void(T)> resolve, std::function<void(TR)> reject){
reject(item);
});
};
template<class T, class TR>
scope<T, TR> scope<T, TR>::then(std::function<void(T, TR)> callback){
if(thenCheck)
callback(resolveValue, rejectValue), thenCheck = false;
return *this;
};
template<class T, class TR>
scope<T, TR> scope<T, TR>::then(std::function<void(T)> callback){
if(thenCheck)
callback(resolveValue), thenCheck = false;
return *this;
}
template<class T, class TR>
scope<T, TR> scope<T, TR>::then(){
return *this;
};
template<class T, class TR>
scope<T, TR> scope<T, TR>::_catch(std::function<void(TR)> callback){
try{
if(catchCheck)
callback(rejectValue), catchCheck = false;
}catch(TR err){
return scope::reject(err);
}
return *this;
}
template<class T, class TR>
T& scope<T, TR>::await(){
if(!thenCheck)
throw std::exception();
thenCheck = false;
return resolveValue;
};
template<class T, class TR>
scope<T, TR>::scope(void){
};
template<class T, class TR>
template<class...types>
scope<T, TR> scope<T, TR>::async(std::function<T(types...)> callback, types...args){
return resolve(callback(args...));
};
namespace ECMA{
template<class T, class TR=T>
using Promise = scope<T, TR>;
// custom lambda wrappers
// template<class TYPE_, class TYPE__, typename...types>
// using wrap = _function<void, _function<void, TYPE_>, _function<void, TYPE__>, types...>;
// template<class TYPE_, typename...types>
// using wrapAsync = _function<TYPE_, types...>;
};