Reputation: 65
I want to convert value of std::variant
to std::string
, but this code doesn't work:
using AnyType = std::variant <bool, char, integer, double, std::string, std::vector <AnyType>/*, Object, Extern, InFile*/>;
struct AnyGet {
AnyGet() {}
std::string operator()(std::string& result, const bool& _ctx) { return _ctx ? "true" : "false"; }
std::string operator()(std::string& result, const char& _ctx) { return std::string(1, _ctx); }
std::string operator()(std::string& result, const integer& _ctx) { return std::to_string(_ctx); }
std::string operator()(std::string& result, const double& _ctx) { return std::to_string(_ctx); }
std::string operator()(std::string& result, const std::string& _ctx) { return _ctx; }
std::string operator()(const std::vector <AnyType>& _ctx, const std::string& _nl = "\n") {/*This depends on to_string*/}
};
std::string to_string(const AnyType& _input, const std::string& _new_line){
std::visit(/*I don't know, what I must write here*/);
}
I want to convert, for example, this: (in code) AnyType some = true;
to (in console) true
.
So, can somebody help me with this?
Upvotes: 2
Views: 1898
Reputation: 679
I variation on @maxin's reply that I find a bit more self contained:
typedef std::variant<unsigned int, double, float, int> VariableData;
typedef std::tuple<unsigned int, VariableData> Variable;//UID, Data
struct VisitPrintVariable
{
void operator()(unsigned int value) { std::cout << std::to_string(value); }
void operator()(double value) { std::cout << std::to_string(value); }
void operator()(float value) { std::cout << std::to_string(value); }
};
static void PrintVariable(VariableData& vd)
{
std::visit(VisitPrintVariable(), vd);
}
Upvotes: -1
Reputation: 136525
A working example:
using AnyType = std::variant<bool, char, int, double, std::string>;
struct AnyGet {
std::string operator()(bool value) { return value ? "true" : "false"; }
std::string operator()(char value) { return std::string(1, value); }
std::string operator()(int value) { return std::to_string(value); }
std::string operator()(double value) { return std::to_string(value); }
std::string operator()(const std::string& value) { return value; }
};
std::string to_string(const AnyType& input) {
return std::visit(AnyGet{}, input);
}
std::vector<std::variant<...>>
as one of std::variant<...>
members requires using a recursive variant type, which is not supported by std::variant
, but supported by boost::variant
.
Upvotes: 5