if/else statement

[CPPprogrammer]

I'm writing a program that is designed to respond to user input. I have one problem at the moment. i need to write a statement that will check the value of a string variable. it's supposed to to the following:

if the variable is equal to "" then it will run a save data function(which i've got sorted.) i'm using dev C++

has anyone got any ideas ?

[MiiNiPaa]

std::string variable;
//...
if (variable == "")
    savedata();
else
   doNothing();

[CPPprogrammer]

Thanks.
Do you possibly know the syntax for a function that accepts variables that i declare outside of it as arguments?

[MiiNiPaa]

Do you just need to pass a copy?
void foo(int x) //Takes integer argument called 'x'
If you need to change it inside:

void bar(int & x) //Takes refetence to int x
{
    x+=10;//x increased by 10 here
}
//...
int a = 5;
bar(a);
std::cout << a;//Prints 15 

[CPPprogrammer]

I need the function to accept string variables as arguments.

[MiiNiPaa]

void foo(intstring x)//Voila
Anything else?

[CPPprogrammer]

Thanks, one more thing.(sorry!)
what is wrong with my code. i keep getting errors like my function has already been defined or something related to my seperate source file which is linked to main.cpp.

below is main.cpp:

// Talk to the Computer V 1.0.0 - this program is designed to respond
// to input from the user.
// main.cpp
// Header files
#include <cstdio>
#include <cstdlib>
#include <iostream>
#include "functions.cpp"
using namespace std;

// Main Program
int main(int nNumberofArgs, char* pszArgs[])
{
string Name;
if(Name == "")
{
cout << "Hello there.\nHave we met?" << endl;
cout << "What's your name?" << endl;
cin >> Name;
Savedata(Name);
cout << "The value of the variable called"
<< "is " << Name << ".\n";
}

// wait until user is ready before terminating program
// to allo user to seee the program results
system("PAUSE");
return 0;
}


and below is functions.cpp (where i store my functions):

// Functons for main.cpp
// functions.cpp
// Standard Template Library Files only
#include <fstream>
#include <string>
using namespace std;

// Savedata Function
void Savedata(string args)
{
ifstream TakeData;
ofstream SaveData;
TakeData.open("data.dat");
TakeData << args;
TakeData.close();
SaveData.open("data.dat");
SaveData >> args;
Savedata.close();
}

[MiiNiPaa]

TakeData << args; //Should be >>
SaveData >> args; //Should be <<
Savedata.close(); //Should be SaveData 

[CPPprogrammer]

Thanks alot, but now i have one problem left. (really really sorry !)
my compiler is saying:

multiple definition of `Savedata(std::string)'
and it is also saying:

first defined here

and

[Build Error] ["Talk] Error 1

[CPPprogrammer]

the compiler is saying from first def..... .......[Build Error]

that the problem is in main.cpp.

[MiiNiPaa]

That means exactlys that: function is defined twice.
I suppose that you have included functions.cpp in project compile list, so there will be 2 SaveData() functions in program: one in compiled functions.cpp and one in main (you included functions.cpp here)

[CPPprogrammer]

I haven't got any other files called functions.cpp and the Savedata() function hasn't been refernced anywhere else in the program

[CPPprogrammer]

I have even deleted all the compiled versions of all the files.

[MiiNiPaa]

So it means that function.cpp in your build list. either delete it from there or create a header for your cpp file and include that in main.
How your code looks after preprocessing:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

/*main.cpp*/ // Talk to the Computer V 1.0.0 - this program is designed t... // to input from the user. // main.cpp // Header files #include <cstdio> //<\ #include <cstdlib> //<--I didn't expand these because they're HUGE #include <iostream>//</ // Functons for main.cpp // functions.cpp // Standard Template Library Files only #include <fstream> #include <string> using namespace std; // Savedata Function void Savedata(string args) //<-First definition { ifstream TakeData; ofstream SaveData; TakeData.open("data.dat"); TakeData << args; TakeData.close(); SaveData.open("data.dat"); SaveData >> args; Savedata.close(); } using namespace std; // Main Program int main(int nNumberofArgs, char* pszArgs[]) { string Name; if(Name == "") { cout << "Hello there.\nHave we met?" << endl; cout << "What's your name?" << endl; cin >> Name; Savedata(Name); cout << "The value of the variable called" << "is " << Name << ".\n"; } // wait until user is ready before terminating program // to allo user to seee the program results system("PAUSE"); return 0; }

/*function.cpp*/ // Functons for main.cpp // functions.cpp // Standard Template Library Files only #include <fstream> #include <string> using namespace std; // Savedata Function void Savedata(string args) //<-Second definition { ifstream TakeData; ofstream SaveData; TakeData.open("data.dat"); TakeData << args; TakeData.close(); SaveData.open("data.dat"); SaveData >> args; Savedata.close(); }

[CPPprogrammer]

is this all working code?
if so shall i delete functions.cpp (the source file)?

[MiiNiPaa]

It is there to show where tjhe problem is.
Methods of solving it here:

So it means that function.cpp in your build list. either delete it from there or create a header for your cpp file and include that in main.

[CPPprogrammer]

I've just put the function into main.cpp and now it all works except the if statement. instead of continuing with the rest of the program it skips to:

system("PAUSE");