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In the following I would like to know how I can convert the cin(in
getline, or using cin directly) for function into a type that uses the
variable 'function', with an actual call to the function display?

So if I enter display ("string here") at the cin prompt it will call
display() and cout string a.

#include <iostream>
#include <string>
using namespace std;

int display (string a)
{cout << a;}

int main()
{
string function;

cout << "< ";
getline(cin,function);
function;



return 0;
}


Thanks,
David

On 31/12/2010 4:30, David Hutto wrote:
> In the following I would like to know how I can convert the cin(in
> getline, or using cin directly) for function into a type that uses the
> variable 'function', with an actual call to the function display?
>
> So if I enter display ("string here") at the cin prompt it will call
> display() and cout string a.
>
> #include<iostream>
> #include<string>
> using namespace std;
>
> int display (string a)
> {cout<< a;}
>
> int main()
> {
> string function;
>
> cout<< "< ";
> getline(cin,function);
> function;
>
>
>
> return 0;
> }
>
>
> Thanks,
> David

There is no simple and elegant way to do this in C++ (that I know of),
for the simple reason that C++ is a compiled language, not an
interpreted one like perl, python or lua.

One option is to maintain a mapping of strings to function pointers,
that is, something like std::map<std::string,int (*)(std::string)>.
Then, you can look up which function corresponds to the one provided by
the user, and call it.
This method has some obvious drawbacks, one of which is that all of the
functions that can be 'called' by the user must have the same method
signature.

The second option is to embed a scripting language in your program. Lua
and python both provide hooks that allow you to embed the scripting
language in your C++ program, and to allow commands in that scripting
language to call your C++ functions.
For more information, see:

http://docs.python.org/c-api/
http://www.lua.org/manual/5.1/manual.html#3

HTH,
Frederik