new for generator does do something useful

[ghost]

RE: https://github.com/tc39/tc39-notes/blob/master/es7/2015-07/july-28.md#67-new--generatorfunction

Actually you can do this :

function *crank() {
    const next = x => this.next( x ),
          turn = x => setTimeout( () => next( x ), 100 );

   let x = 1;
   while( true ) console.log( x = x < 12 ? yield turn( x + 1 ) : yield turn( 1 ) );
}

Having a reference to itself, allows the generator to yield control flow to other operation, before returning to itself and continue processing.

This is useful.

const count = new crank();
count.next(); // yay!

Without [[construct]] trap for generators this is required:

function *crank() {
    const my = yield 'MPs EYE BAN ON NEW FOR COROUTINES AS CONSIDERED "HARMFUL"',
        next = x => my.next( x ),
        turn = x => setTimeout( () => next( x ), 100 );

   let x = 1;
   while( true ) console.log( x = x < 12 ? yield turn( x + 1 ) : yield turn( 1 ) );
}

const inconvenient = crank();
inconvenient.next();
// harmful you say?
inconvenient.next( inconvenient ); // qed

[claudepache]

Just use a wrapper.

function start_counter() {

    function* crank() {
        const next = x => count.next( x ),
              turn = x => setTimeout( () => next( x ), 100 );

       let x = 1;
       while( true ) console.log( x = x < 12 ? yield turn( x + 1 ) : yield turn( 1 ) );
    }

    const count = crank();
    count.next(); 
}

start_counter(); // implementation details hidden: no "new", no "next"

Anyway, that sort of discussion should go to the es-discuss mailing list.

[domenic]

Closing this per https://github.com/tc39/ecma262/blob/master/CONTRIBUTING.md#feature-requests