[Issue 7177] $ should forward to length by default

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=7177



--- Comment #29 from Steven Schveighoffer <schveiguy at yahoo.com> 2013-03-21 12:47:14 PDT ---
(In reply to comment #28)
> Yeah, exactly what he said. Having yet another trait means:
> a) Don't test the trait and ignore opDollar.

By your own definition (1. we don't check for it, and 2. you can't write
generic code with $), that is exactly what is done now.

> b) Test the trait and fork the code even more.

Huh?  If your algorithm requires opDollar, use it.  If not, then it didn't
exist before.  Where is the forking?

I looked at isRandomAccessRange.  It can be true if the range is infinite,
which most likely do NOT define $.  If that is the case, how can generic code
use $ simply if isRandomAccessRange is true?

> What we are trying to do is:
> a) Not break code by adding more to the requirements.

Wait, I thought we are adding opDollar to the requirements?

> b) Provide an external solution for ranges that don't define opDollar (because
> for a range, defining opDollar as an alias of length IS natural).

As I previously stated, I don't have a problem with this, as long as it only
applies to ranges you define, and NOT ranges or types where it makes no sense.

1. opDollar is NOT equivalent to length in all cases.  Therefore, making it
equivalent by default BY DEFINITION breaks existing code that purposely defines
length and purposely omits opDollar.
2. Adding opDollar requirements to range traits requires all existing ranges
that could define opDollar DO define opDollar.
3. You wish to avoid immediate breakage of code that has not yet implemented
opDollar but satisfies current implementation of said traits.

So in other words your goal is to break existing code so other existing code
doesn't break?

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