On 4/2/18 3:24 PM, Cym13 wrote:
On Monday, 2 April 2018 at 18:33:25 UTC, Steven Schveighoffer wrote:
On 3/30/18 4:45 PM, Cym13 wrote:
On Friday, 30 March 2018 at 20:43:09 UTC, Cym13 wrote:
Hi, I've got the following code that takes a list of files as
argument and xor them together (demo example sufficient for that
discussion).
[...]
Forgot to mention but I'm also quite annoyed at the need for that
".array" because "transposed" requires the RoR to be assignable. That
kills the laziness. I'm very much open to suggestions regarding that
point.
1. The .save deprecation may not affect you. It's probably being used
by map or fold but may not need to be. Once it's removed, you may just
see the warning go away, and everything still works just fine. I'm not
100% sure on this, as I don't know where it's being used.
That's good to hear, although I don't realy like warnings on which I
have no control.
Well, it's tough, because you can compose ranges in infinite ways. All
you need to generate the warning is some code like this:
static if(is(typeof(r.save)) r.save;
And now, even if you're not supposed to use it, it gets used. But if
there is a fallback implementation when save *isn't* available, then it
will still work when the deprecation becomes an error.
Caveat here is that I don't know if this is a case in your example. But
if it is working how you expect (and I believe it does), then it should
continue to work. If not, file an issue when that happens.
2. The array is necessary, as map is lazy. what you want is a range of
the first byte of each file, then a range of the second byte of each
file, etc. mapping to a byte array can't possibly do this, because
what would happen is that map would re-open the file, re-read it's
contents, and then give you the *second* byte. This is horribly
inefficient.
While I agree that using an array is ugly, and that I want ranges of
first byte (which is why I'm using transposed in the first place),
transposed just doesn't let me work with the result of map itself. I
suppose it's because its signature stipulates hasAssignableElements. I
feel like I'm missing something there but I can't see what.
Let's simplify it into an array of arrays:
int[][] x = [[1,2,3],[4,5,6],[7,8,9]];
In order to progress the transposed wrapper, you need to "popFront" each
element in the array. Which means you need to traverse the array,
getting each element, getting the front of *that* element, and then
popping it off and assigning it back. In other words, after one
popFront, it should look like this:
[[2,3],[5,6],[8,9]]
If you can't assign the range back to itself, then it can't be made to
progress -- you would simply just get the first front over and over again.
The fact that you have to reassign the elements belies why save can
never be made to work -- you have to overwrite the original!
-Steve
