Question

How to use preprocessor ## to concatenate the left and right sides in C

Answer 1

#include <stdio.h>

#define CONCATENATE(a, b) a##b

int main()
{
    printf("%d", CONCATENATE(12, 90));

    return 0;
}



/*
run:

1290

*/

 

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Answer 2

#include <stdio.h>

#define CONCATENATE(a, b) a##b

int main()
{
    printf("%f", CONCATENATE(3.14, 999));

    return 0;
}



/*
run:

3.149990

*/

 

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