macro function

[mar11]

Hi all,

look at this function...

#include <string>
#include <iostream>

 string TEST1(string str){
  
 str.append("my string");
  
 return str;
 }

int main(){
string stri;
stri = TEST1("this string is ");  cout << stri<<endl;
}  // output -- this string is my string 

Now, how can i implement this function as macro and how will be returned..

please can you explain it through executable example

thanks for each support

[kevinchkin]

I would suggest use inline functions instead.

inline string TEST1(string str) { 
return str.append("my string"); 
}

[mar11]

Acually, i know that i can use the inline function.. but i am interessted to know how the returned functions could be implemented as macro..

could anybody explain me that?

thanks alot

[Duthomhas]

A macro is just a text-replacement.

Given the source code:

#define PI 3.141592

cout << PI << endl;

The C preprocessor replaces every instance of "PI" with the text "3.141592". The compiler then sees the source code as:

cout << 3.141592 << endl;

Macro functions work the same way. To make your macro function, work in reverse.

string str = "this string is ";
string stri;
stri = str.append( "my string" );
cout << stri << endl;

becomes

#define TEST1( s ) s.append( "my string" )

string str = "this string is ";
string stri;
stri = TEST1( str );
cout << stri << endl;

There is an important thing about macro arguments -- they are simple text substitutions. You cannot treat them like you did above.

There is, however, a simple macro trick to concatenate strings.

#include <iostream>
using namespace std;

#define CATS( s ) s "my string"

int main()
  {
  cout << CATS( "this string is " ) << endl;
  return 0;
  }

which becomes:

#include <iostream>
using namespace std;



int main()
  {
  cout << "this string is " "my string" << endl;
  return 0;
  }

Hope this helps.