On Sun, Aug 12, 2012 at 5:56 PM, Brian Moon <br...@moonspot.net> wrote:
> On 8/12/12 5:33 PM, Levi Morrison wrote:
>>
>> On Sun, Aug 12, 2012 at 2:08 PM, Brian Moon <br...@moonspot.net> wrote:
>>>
>>> Do you have a good example usage other than a file? I don't find
>>> fopen/fgets/fclose all that complicated. What are the other valid use cases
>>> for such a thing?
>>
>>
>> One fabulous use case is creating an iterator for a Binary Search
>> Tree. A post order done without generators looks like:
>>
>> https://github.com/morrisonlevi/PHP-Datastructures/blob/master/src/Spl/PostOrderIterator.php.
>> An iterator using a generator looks something like:
>>
>> public function getIterator() {
>> if ($this->left) yield* $this->left;
>> yield $this->value;
>> if ($this->right) yield* $this->right;
>> }
>>
>> This is 5 lines. The fully commented version of the post-order
>> iterator previously mentioned is 106 lines of code and is considerably
>> harder to understand.
>
>
> Well, it's 52 lines, not 106. The 5 lines above are not commented nor are
> they spaced at all like the ones in the class.
No, Brian, it is 106 lines of actual code I would find in the wild.
And sure, I'd have spaced the generator code more like:
public function getIterator() {
if ($this->left) {
yield* $this->left;
}
if ($this->right) {
yield* $this->right;
}
yield $this->value;
}
However, that's 11 lines of code compared to 106.
> In the above example, what
> sets $this->right? or $this->left?
Iterators don't set $this->right and $this->left; they only traverse the tree.
> I don't consider this a very good example.
That's fine. You are entitled to your opinion. However, you didn't
have to figure out the 106 lines of code that is the Post-Order
iterator. That was a NIGHTMARE and I'm still not 100% confident that
it works as it is supposed to. The generator, on the other hand, is
simple and follows the definition very closely. MUCH better.
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