View Compilation Error

0_0_26769879_26572.cpp: In function 'int main()':
0_0_26769879_26572.cpp:9:12: error: 'swap' was not declared in this scope
    swap(a,b);
            ^
0_0_26769879_26572.cpp:13:12: error: 'swap' was not declared in this scope
    swap(a,c);
            ^
0_0_26769879_26572.cpp:17:12: error: 'swap' was not declared in this scope
    swap(b,c);
            ^