make variable1+variable2 into var1var2() func ?

[Tropod]

hi,

I was wondering if/is there a way to turn/use 2 char/string variables, join them, and then use the (joined) variable to call a function ?

For example;

char *varA, *varB; //char variables taken from a table based on user input.
char *varAB;

//where varAB == varA+varB & subsequently calls different varAB functions

void varAB1(double)
{
    //do function;
}

void varAB2(double)
{
    //do function;
}

I've tried using this (& hopefully shows more clearly what I'm 'trying' to do);

#define fPrint1(VAR,double) f ## VAR ## PRINT2(double)
#include <iostream>
void fONEPRINT2(double &);
void fTWOPRINT2(double &);

int main()
{
  char *table[] = {"ONE", "TWO", "THREE", "FOUR"}; 
  char *TABLE = table[1];
  double i=100;
  fPrint1(TABLE,i);
  std::cin.get();
}

void fONEPRINT2(double &i)
{
  std::cout<<"fONEPrint\n";
  std::cout<<i;
}

void fTWOPRINT2(double &i)
{
  std::cout<<"fTWOPrint\n";
  std::cout<<i;
}

But fPrint1(TABLE,i) always seems to take on the literal meaning TABLE, when I want it to take on its meaning in the *table[] & use that string in order to call the function.

Just wondering if such a thing is possible, & if so how, or do the functions need to be called by their literal names.


Any tips/pointers etc appreciated, thanks.
p.s. still learning.

[sean]

you can use strcat() to join two strings - but I'm a little confused as to what you're trying to do - it seems like you want to join two strings together and call a method by that name. It doesn't work so directly - but you could compare the strings to known possibilities and when you find a match, you call that function.

Pseudocode:

c = a + b;
if(c == "one") one();
if(c == "two") two();

[Tropod]

Thanks for the suggestion.
Yes, wanting to join two string variables & then call a method using the joined string.
It's exactly what I am wanting to do, but I would prefer if I didn't have to resort to 100+ switches or if statements, which is why I ask if such a thing is somehow possible.

[anon]

It is also possible to use, for example, an array of function pointers, or a map<string, function pointer>.

However, normally identifiers don't exit at runtime. You can't concatenate identifiers at runtime and use them.

If it is not absolutely mandatory to use C++ for this, scripting languages that are aware of all identifiers at runtime make it much easier. E.g in Python:

def foobar():
    print 'Hello world'

if __name__ == '__main__':
    a = raw_input("First part of function name (preferably foo):")
    b = raw_input("Second part of function name (preferably bar):")
    try:
        eval(a + b + "()")
    except:
        print "No such luck"