what does cout << “\n”[a==N]; do?

Question

In the following example:

cout<<\"\\n\"[a==N];

I have no clue about what the [] option does in cout, but it

Answer 1

It is not an option of cout but an array index of "\n"

The array index [a==N] evaluates to [0] or [1], and indexes the character array represented by "\n" which contains a newline and a nul character.

However passing nul to the iostream will have undefined results, and it would be better to pass a string:

cout << &("\n"[a==N]) ;

However, the code in either case is not particularly advisable and serves no particular purpose other than to obfuscate; do not regard it as an example of good practice. The following is preferable in most instances:

cout << (a != N ? "\n" : "") ;

or just:

if( a != N ) cout << `\n` ;