Is “else if” a single keyword?

Question

I am new to C++. I often see conditional statement like below:

if 
  statement_0;
else if
  statement_1;

Question:

Syntacticall

Answer 1

Syntactically, it's not a single keyword; keywords cannot contain white space. Logically, when writing lists of else if, it's probably better if you see it as a single keyword, and write:

if ( c1 ) {
    //  ...
} else if ( c2 ) {
    //  ...
} else if ( c3 ) {
    //  ...
} else if ( c4 ) {
    //  ...
} // ...

The compiler literally sees this as:

if ( c1 ) {
    //  ...
} else {
    if ( c2 ) {
        //  ...
    } else {
        if ( c3 ) {
            //  ...
        } else {
            if ( c4 ) {
                //  ...
            } // ...
        }
    }
}

but both forms come out to the same thing, and the first is far more readable.