C++ MultiLine #if

Question

I've been trying to google this for a while now but I can't seem to be able to find any clear answer if it can be done at all.

I wanted to know if it's possible to do a MultiLine #if statement in C++ in a similar way to this type of if

if (
   1 == 1 ||
   2 == 2 ||
   3 == 3
) {
   cout << "True\n";
}

I was hoping for something along the lines of (which I know is hopelessly wrong)

#if
   1 == 1 ||
   2 == 2 ||
   3 == 3
#then
   cout << "True\n";
#else
   cout << "False\n";
#endif

Answer 1

#if \
   1 == 1 || \
   2 == 2 || \
   3 == 3
   cout << "True\n";
#else
   cout << "False\n";
#endif

Backslash-newline combinations are stripped very early in preprocessing, even before tokenizing the input. You can use this to spread preprocessor directives across multiple physical lines.

Heck, you could theoretically even do

#i\
f 1 == 1 |\
| 2 == 2 || 3 =\
= 3

but then your colleagues might get upset with you.

Answer 2

Yes. With continuation lines:

#if \
   1 == 1 || \
   2 == 2 || \
   3 == 3
   cout << "True\n";
#else
   cout << "False\n";
#endif