On Sunday, 18 March 2018 at 20:07:28 UTC, Jonathan M Davis wrote:
On Sunday, March 18, 2018 14:56:04 Steven Schveighoffer via
Digitalmars-d wrote:
On 3/18/18 2:24 PM, Jonathan M Davis wrote:
> On Sunday, March 18, 2018 13:10:28 Steven Schveighoffer via
> Digitalmars-d
>
> wrote:
>> On 3/18/18 4:34 AM, sdvcn wrote:
>>> dchar v11=dchar.max;
>>>
>>> auto vp11 = [v11];
>>>
>>> auto v2 = cast(ubyte[]) (vp11); //v2.length=4
>>> auto v22 = cast(ubyte[])( [v11]); //v2.length=1
>>
>> This seems like a bug to me.
>>
>> It appears that v22 has truncated v11 to a byte and made
>> only a single byte array out of it.
>
> Except that that's precisely how you usually get an array
> any integral type smaller than an integer. e.g.
>
> auto arr = cast(ubyte[])([1, 2, 3, 4]);
>
> In this case, you could do
>
> ubyte[] arr = [1, 2, 3, 4];
>
> instead, but if you're not dealing with an initializaton or
> assignment like this (e.g. you're passing the array to a
> functon), then the cast is the way you do it. Normally, you
> do it with integer literals, and I could see an argument
> that it shouldn't allow it without VRP being used to make it
> work, but it _is_ a cast, and casts are a bit of a blunt
> instrument.
>
> So, I really don't think that it's a bug.
It's quite possible that you aren't understanding what is
happening:
ubyte[] arr = cast(ubyte[])[555];
writeln(arr); // [43]
Why is this not a bug? I didn't cast the 555 to a ubyte, so it
should either complain that it can't do it, or give me an
array of 4 bytes.
I guess it could be explained as the same thing as:
ubyte[] arr = [cast(ubyte)555];
But this is surprisingly weird behavior.
That's exactly what it's doing, and when you have multiple
elements in the literal, it quickly gets a lot more pleasant
than casting each element individually. e.g.
cast(ubyte[])[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
vs
[cast(ubyte)0, cast(ubyte)1, cast(ubyte)2, cast(ubyte)3,
cast(ubyte)4,
cast(ubyte)5, cast(ubyte)6, cast(ubyte)7, cast(ubyte)8,
cast(ubyte)9,
cast(ubyte)10]
I use this trick all the time when creating arrays of integral
types smaller than int, precisely because casting each element
is a royal pain and way harder to read.
- Jonathan M Davis
代码目的是转换任意类行到ubyte[]
The object of the code is to convert any class of rows to ubyte[]
但是非数组类无法正确转化
But non - array classes can't be converted correctly
void pByte(T)(T v)
{
ubyte[] uBuf;
static if(isArray!T){
uBuf = cast(ubyte[])mKey;
}else{
uBuf = cast(ubyte[])[v];
}
writeln(uBuf);
}
无法得到正确结果
Unable to get the correct result
