CODEWITHSUNDEEP
clinuxgccc-preprocessor
ART
ART

Reputation: 1579

Add two macro and convert to string in pre-processing stage

I want to add two macro definition and want to convert result into string in pre-processing stage itself i tried it in following ways but it doesn't work

#include <stdio.h>

#define TO_STRING_IND(arg) #arg
#define TO_STRING(arg)  TO_STRING_IND(arg)

#define ABC 1
#define XYZ 2
#define TOTAL (ABC+XYZ) 
#define total_str TO_STRING(TOTAL)


int main()
{
        printf("total %d \n",TOTAL);
        printf("total_str %s \n",total_str);
        return 0;
}

output of this program is as follows,

total 3 
total_str (1+2)

I expect total_str to be 3 in string.

Any suggestions ?

Upvotes: 1

Views: 202

Answers (3)

BLUEPIXY
BLUEPIXY

Reputation: 40155

You can in addition preprocessor in the range of up to 256(BOOST_PP_LIMIT_MAG) if You can use the boost.

#include <stdio.h>
#include <boost/preprocessor/arithmetic/add.hpp>

#define TO_STRING_IND(arg) #arg
#define TO_STRING(arg)  TO_STRING_IND(arg)

#define ABC 1
#define XYZ 2
#define TOTAL (ABC+XYZ) 
#define total_str TO_STRING(BOOST_PP_ADD(ABC, XYZ))


int main()
{
    printf("total %d \n",TOTAL);
    printf("total_str %s \n",total_str);
    return 0;
}

Upvotes: 2

Sathish
Sathish

Reputation: 3870

(ABC+XYZ) this will be replaced by (1+2). Then the TOTAL in your Program will be replaced by (1+2).

so printf("total %d \n",(1+2)); this will add the number and gives the output as 3.

But total_str will be replaced by "(1+2)", where (1+2) is a string.

The reason is TO_STRING((1+2)) will be replaced by #(1+2). # is Stringizing operator. it will convert the argument to string.

printf("total_str %s \n","(1+2)"); it can't add (1+2) because it is a string.

so you will get the result as (1+2).

Upvotes: 1

Matthias
Matthias

Reputation: 1352

The only place where the preprocessor does any calculation is in #if statements. Otherwise the preprocessor makes only textual replacements. Therefore it cannot be done in the preprocessor stage what you are trying to do.

Upvotes: 1

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