yield iteration

[bearophile]

anonymous:

> A subthread of the "Impressed" thread revolved around D's lack 
> of a yield mechanism for iteration.

The yield as in Python is so useful and handy, and I miss it 
often in D.

This is an example of Inverse Gray iterator (Sloane series 
A006068) Python2 code from:
http://code.activestate.com/recipes/221457/

def A006068():
     yield 0
     for x in A006068():
         if x & 1:
             yield 2 * x + 1
             yield 2 * x
         else:
             if x:
                 yield 2 * x
             yield 2 * x + 1


Turning that in D code that uses opApply is not hard, but the 
code inflates 3X, and you can't use most std.algorithm on it.

I have discussed the situation a little here:
http://d.puremagic.com/issues/show_bug.cgi?id=5660

Bye,
bearophile