Friday, 3 July 2009

C++ Syntax Puzzle

This is an interesting puzzle and possibly an interiew question:

Without attempting to compile it, is the following code compilable? Is t in scope in the if body or the else?


#include <iostream>

using namespace
std;

int
returnanint() {
return
1;
}


using namespace
std;
int
main(int argc, char * argv[])
{

if
(int t=returnanint()) {
cout << "t > 0 = " << t << endl;
}

else
{
cout << "t==0 " << endl;
t++;
}

return
0;
}


Answer below
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The answer is, yes it compiles. It's an interesting and certainly not intuitive gray area of C++. The int is declared outside of the braces following the if so is in scope for both those braces and those for the else branch.

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