Tentative coroutine syntax

gistfile1.m

#define coroutine(ARGS) \
	__block unsigned long ext_coroutine_line_ = 0; \
	\
	return ^(ARGS){ \
		for (;; ext_coroutine_line_ = 0) \
			switch (ext_coroutine_line_) \
				default:

#define return_coroutine \
	}

#define yield \
	if ((ext_coroutine_line_ = __LINE__) == 0) \
		case __LINE__: \
			; \
	else \
		return

id myCoroutine =
	^{
		__block int myVariable = 5;

		coroutine(int n) {
			// do stuff
			yield 5 + n;

			// do more stuff
			yield ++myVariable;
		}

		return_coroutine;
	}();

this is very tricky And obscure...
I was trying to expand the macros, only to find it was more confusing...
//===before expand

__block int i;

    int (^myCoroutine)(void) = coroutine(void)({
        for (i = 0;i < 3;++i) {
            NSLog(@"%@",@(i));
            yield i;
        }
    });

//after expanding

int (^myCoroutine)(void) =  ^{ 
     __block unsigned long ext_coroutine_line_ = 0; 

    ^(void) { 
        for (;; ext_coroutine_line_ = 0) 
            switch (ext_coroutine_line_) 
                default: 
                for (i = 0;i < 3;++i) {
                    if ((ext_coroutine_line_ = __LINE__) == 0)
                        case __LINE__: 
                    ; 
                    else 
                        return i;
        } 
            } 
    }()


  ({
        for (i = 0;i < 3;++i) {
            if ((ext_coroutine_line_ = __LINE__) == 0)
                case __LINE__: 
                ; 
            else 
                return i;
        }
    });