Map Function

Here is the question:

I want to call some functions that are the same type and use a variable or a property to selects these functions.
At sometimes, I can use the switch struct to do it. But sometimes, I can not! For example: the type of the variable
is a string(like this: switch ("mystring") { ... }).

In this case, I think you can try the map function to do it.

At first, We need to define some types:

typedef float optfunc_t(float a, float b);
typedef std::map<std::string, optfunc_t*> strfmap_t;

As you seeing, The optfunc_t is type of our functions and We can call these functions by a variable that type of strfmap_t:

float plus(float a, float b)
{
    return a + b;
}

float minus(float a, float b)
{
    return a - b;
}

int main()
{
    strfmap_t m;
    m["plus"] = plus;
    m["minus"] = minus;

    std::cout << m["plus"](100.01, 10.001) << std::endl;
    std::cout << m["minus"](100.01, 10.001) << std::endl;

    return 0;
}

In the above code. We create a variable m and set two pairs of string and function. These operations are very simple. Let us to call it.

Here is the fully code:

#include <iostream>
#include <map>
#include <string>


typedef float optfunc_t(float a, float b);
typedef std::map<std::string, optfunc_t*> strfmap_t;


float plus(float a, float b)
{
    return a + b;
}

float minus(float a, float b)
{
    return a - b;
}


int main()
{
    strfmap_t m;
    m["plus"] = plus;
    m["minus"] = minus;

    std::cout << m["plus"](100.01, 10.001) << std::endl;
    std::cout << m["minus"](100.01, 10.001) << std::endl;

    return 0;
}