On Sunday, 23 August 2015 at 13:46:30 UTC, anonymous wrote:
On Sunday 23 August 2015 12:17, Doolan wrote:
And the use of auto everywhere makes it really hard to tell
what types I should be using for anything. My compiler talks
about RangeT!(whatever) but you try to use RangeT!(whatever)
and you find out RangeT is private...
You can use typeof to get the type of a range expression when
typing it out is impractical/impossible.
What if I want to save a range in a struct? Or is a range more of
a verb than a noun..?
Can someone give me a short summary of how to use ranges?
I'm not sure what exactly you're looking for. The documentation
for tee has some example code. How about you show something
you're having trouble with?
The possibility of using ranges comes up a lot, but here's
today's example:
I need to compress some data, and luckily it's very suited for
Running Length Encoding, so I've gone with doing that.
Occasionally changes need to be made to this data and so rather
than extracting the data, changing it, and then recompressing it,
I can just do the equivalent of leaving a post-it note reminding
the decompression function to sprinkle these changes in after
decompression. Occasionally, I also need to grab some values out
of this data without decompressing it, but for every additional
value I look for I have to search the post-it notes and it gets a
little fiddly.
So, I vaguely know what ranges are, and I've heard you can chain
them together, and my code would be much more readable if I could
cut up access to the data and splice in changes... but I don't
even know how to define a range of the right type...
And how do they relate to slices? That line is really blurry...
"Slice" is a synonym for what the spec calls a "dynamic array",
i.e. a structure containing a pointer and a length.
"Slicing" a dynamic array, static array, or pointer produces a
dynamic array, referencing (not copying) the sliced elements:
----
int[] d = [1, 2, 3, 4]; /* dynamic array */
int[] slice = d[1 .. 3];
assert(slice == [2, 3]);
d[1] = 20;
assert(slice[0] == 20);
int[4] s = [1, 2, 3, 4]; /* static array */
slice = s[];
assert(slice == [1, 2, 3, 4]);
int* p = [1, 2, 3, 4].ptr; /* pointer */
slice = p[1 .. 3];
assert(slice == [2, 3]);
----
Note that the source types are different, but slicing them
yields the same type every time: int[].
Generally, dynamic arrays / slices are random-access ranges.
Narrow strings (string/wstring/char[]/wchar[]/...) are a
notable exception to this. They are dynamic arrays of
UTF-8/UTF-16 code units. But they're not random-access ranges
of Unicode code units. Instead, they're _forward_ ranges of
Unicode code _points_ (dchar). They have special range
primitives that to the decoding.
So slices are random-access ranges... I understand the
random-access part... but are they inheriting from Range, do they
just include a Range? Why is int[] an array when I declare, but
variable[] a Range?? Or isn't it a Range?
