Function calls

[Lutger]

On 01/28/2010 11:28 PM, Andrei Alexandrescu wrote:
> Lutger wrote:
>> On 01/28/2010 11:05 PM, Andrei Alexandrescu wrote:
>>> Michiel Helvensteijn wrote:
>>>> Andrei Alexandrescu wrote:
>>>>
>>>>>>> foreach (line; stdin.byLine()) { ... }
>>>>>>>
>>>>>>> vs.
>>>>>>>
>>>>>>> foreach (line; stdin.byLine) { ... }
>>>>>>>
>>>>>>> How do I choose?
>>>>>> byLine is a property. It is fetching a range on stdin.
>>>>>>
>>>>>> -Steve
>>>>> Damn. I was sure the answer will be different.
>>>>
>>>> byLine() is a function. It changes the state of stdin. Calling it
>>>> consecutively will in general result in different return values. If
>>>> there
>>>> were two guys: stdin.currentLine (property) and stdin.nextLine(), it
>>>> would
>>>> be a different story.
>>>>
>>>> A property should act very much like a field. The advantages of
>>>> properties
>>>> are that they can be derived (not have a one-to-one relation with a
>>>> storage
>>>> location) or can do some clever caching/memoizing/logging.
>>>
>>> I agree, but I'll also note that I got contradictory opinions from
>>> different supporters of @property. So now it looks all the more like a
>>> judgment call, which is exactly what I was worried in the first place.
>>>
>>>> Omitting parentheses on an action just because you can is stupid. It
>>>> actually makes the language less readable and less predictable. And all
>>>> that for saving two keystrokes.
>>>
>>> I found my code to be more readable and just as predictable with the
>>> current rule. And it's not about two keystrokes, it's about persistent
>>> and ubiquitous syntactic noise.
>>>
>>> Gosh, @property does suck. I was afraid that'd be true.
>>>
>>>
>>> Andrei
>>
>> Lot's of things are judgement calls, I don't see the problem.
>> @property is a tool like everything else, there are many more cases
>> where it's pretty clear cut. The ambivalence here is inherent in the
>> code, and only brought out by the @property question, not caused by
>> it. Notice there was also no consensus of what byLine actually did
>> under the hood.
>>
>> Also, don't forget these:
>> - @property allows you to forbid the caller using parenthesis, there
>> is no other way in D to achieve this for accessor functions
>> - so far ignored in this thread: any kind of code inspection
>> (reflection, compile time, by IDE) can use the '@property property'
>> for various purposes.
>
> Wise words. So how do I go about byLine?
>
> Andrei

You make a good judgement call :)

this is possible right:

auto iter = stdin.byLine; foreach(line; iter) ...

could you imagine byLine as an abbreviation of byLineRange or 
getByLineRange a la Java?

or even conceive of: stdin.byLine = aDifferentFlavorOfByLine?

So yes, I'm inclined to think of it as a property.