Question:

How can type-insensitive macros be created?

Answer:

A type-insensitive macro is a macro that performs the same basic operation on different data types. This task can be accomplished by using the concatenation operator to create a call to a type-sensitive function based on the parameter passed to the macro. The following program provides an example:

#include <stdio.h>
#define SORT(data_type) sort_ ## data_type
void sort_int(int** i);
void sort_long(long** l);
void sort_float(float** f);
void sort_string(char** s);
void main(void);
void main(void)
{
     int** ip;
     long** lp;
     float** fp;
     char** cp;
     ...
     sort(int)(ip);
     sort(long)(lp);
     sort(float)(fp);
     sort(char)(cp);
     ...
}

This program contains four functions to sort four different data types: intlongfloat, and string (notice that only the function prototypes are included for brevity). A macro named SORT was created to take the data type passed to the macro and combine it with the sort_ string to form a valid function call that is appropriate for the data type being sorted. Thus, the string

sort(int)(ip);

translates into

sort_int(ip);

after being run through the preprocessor.


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