Serialization

`BOOST_STRONG_TYPEDEF`

Motivation

typedef creates an alias for an existing type. It does not create a new type that can be used for matching either function or template parameters. This can be shown by trying to compile the following example.


typedef int a;
void f(int x);  // (1) function to handle simple integers
void f(a x);    // (2) special function to handle integers of type a 
int main(){
    int x = 1;
    a y;
    y = x;      // other operations permitted as a is converted as necessary
    f(x);       // chooses (1)
    f(y);       // chooses (2)
}

Since typedef doesn't create a new type, this program can't compile to code that implements its obvious intention.

Usage of BOOST_STRONG_TYPEDEF addresses this.



#include <boost/strong_typedef.hpp>


BOOST_STRONG_TYPEDEF(int, a)
void f(int x);  // (1) function to handle simple integers
void f(a x);    // (2) special function to handle integers of type a 
int main(){
    int x = 1;
    a y;
    y = x;      // other operations permitted as a is converted as necessary
    f(x);       // chooses (1)
    f(y);       // chooses (2)
}

The program will now compile and run as expected.

Usage

Syntax of BOOST_STRONG_TYPEDEF has been designed to be similar to the standard typedef. So


BOOST_STRONG_TYPEDEF(primitive type, name)

will create a new type "name" which will be substitutable for the original type but still of distinct type.

Implemenation

BOOST_STRONG_TYPEDEF is a macro which generates a class named "name" wraps and instance of its primitive type and provides appropriate conversion operators in order to make the new type substitutable for the one that it wraps.

Revised 31 March, 2004