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c++stdmapassignment-operatorstd-variant

Assignment operator for std::variant

I'm trying to assign a float to a defined value in my std::map using std::variant. I initialized my map this way:

std::map<std::string,std::variant<float,int,bool,std::string> kwargs; 
kwargs["type"] = "linear"; 
kwargs["flag"] = true; 
kwargs["height"] = 5; 
kwargs["length"] = 4.5;

I'm trying to archive this operation:

float f = kwargs["length"]; 
float a = f+0.5;

How can I transfer std::map key into a float for simple arithmetic operation?

Solution

  • To access the variant, you need to use the free function std::get:

    float f = std::get<float>(kwargs["length"]);

    Also, you might run into a problem with this line:

    kwargs["length"] = 4.5;

    Since 4.5 is a literal of type double, and not float. To solve this, just use the F suffix:

    kwargs["length"] = 4.5F;