Question

I’ve problem to merge 3 variable become in to one variable:

example :

int var1,var2,var3;
int result;
var1 = 1;
var2 = 2;
var3 = 3;

result = ........??;

printf("Result %d",result);

output :
123

How can I do this?

Answer 1

Yay, C++11 variadic templates are awesome! Here’s a N-finitely expandable version, assuming sum(args) < INT_MAX

template<int max, int ...arguments>
int merge_integers()
{
    int args[] = { arguments... };
    int size = sizeof(args) / sizeof(int);
    int mul = 1;
    int result = 0;

    for (int i = size; i--; )
    {
        result += args[i] * mul;
        mul *= max;
    }

    return result;
}

Example usage:

printf("%d\n", merge_integers<10, 5, 4, 3, 2, 1>());
printf("%x\n", merge_integers<16, 0xA, 0xB, 0x1, 0x3, 0x5>());
printf("%o\n", merge_integers<8, 1, 2, 3, 4, 7>());

Output:

54321
ab135
12347