Handling arbitrary char ranges
ag0aep6g via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Wed Apr 20 15:44:37 PDT 2016
On 20.04.2016 23:59, Alex Parrill wrote:
> On Wednesday, 20 April 2016 at 17:09:29 UTC, Matt Kline wrote:
>> [...]
>
> First, you can't assign anything to a void[], for the same reason you
> can't dereference a void*. This includes the slice assignment that you
> are trying to do in `buf[0..minLen] = remainingData[0..minLen];`.
Not true. You can assign any dynamic array to a void[].
Regarding vector notation, the spec doesn't seem to mention how it
interacts with void[], but dmd accepts this no problem:
----
int[] i = [1, 2, 3];
auto v = new void[](3 * int.sizeof);
v[] = i[];
----
[...]
> Second, don't use slicing on ranges (unless you need it). Not all ranges
> support it...
As far as I see, the slicing code is guarded by `static if (isArray!T)`.
Arrays support slicing.
[...]
> Instead, use a loop (or maybe `put`) to fill the array.
That's what done in the `else` path, no?
> Third, don't treat text as bytes; encode your characters.
>
> auto schema = EncodingScheme.create("utf-8");
> auto range = chain("hello", " ", "world").map!(ch => cast(char) ch);
>
> auto buf = new ubyte[](100);
> auto currentPos = buf;
> while(!range.empty && schema.encodedLength(range.front) <=
> currentPos.length) {
> auto written = schema.encode(range.front, currentPos);
> currentPos = currentPos[written..$];
> range.popFront();
> }
> buf = buf[0..buf.length - currentPos.length];
You're "converting" chars to UTF-8 here, right? That's a nop. char is a
UTF-8 code unit already.
> (PS there ought to be a range in Phobos that encodes each character,
> something like map maybe)
std.utf.byChar and friends:
https://dlang.org/phobos/std_utf.html#.byChar
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