Appenders and Arrays

[default0 via Digitalmars-d-learn]

On Tuesday, 1 September 2015 at 17:20:49 UTC, Steven 
Schveighoffer wrote:
> On 9/1/15 12:49 PM, default0 wrote:
>> Hello
>>
>> A simple thing I stumbled across:
>>
>> int main()
>> {
>>      import std.stdio;
>>      import std.range;
>>
>>      int[] d;
>>      d ~= 10;
>>      d ~= 20;
>>      d.put(5);
>>      writeln(d);
>>
>>      return 0;
>> }
>>
>> Appenders work fine as output ranges, but arrays do not. The 
>> above code
>> prints "20" (ie the 10 is removed). Is "put" not supposed to 
>> mean
>> "append one element"?
>
> put into an slice does not append, it fills in the front. This 
> is because the "target" of a slice is the data it points at.
>
> Think of it as a buffer that you want to fill:
>
> int[20] buf;
> int[] outputRange = buf[];
> outputRange.put(10);
> outputRange.put(20);
>
> assert(buf[0..2] == [10,20]);
>
>> Further, while the following compiles fine but runs really 
>> odd, the
>> following does not compile:
>>
>> int main()
>> {
>>      import std.stdio;
>>      import std.range;
>>
>>      char[] c;
>>      c ~= 'a';
>>      c ~= 'b';
>>      c.put('c');
>>      writeln(c);
>>
>>      return 0;
>> }
>>
>> C:\dmd\src\phobos\std\range.d(9,9): Error: static assert  
>> "Cannot put a
>> char into a char[]." (Test)
>>
>> I am puzzled by
>> 1) Why I cannot put a char into a char[] (even though I can 
>> totally
>> append them)
>
> That seems like a bug. put has specific code to deal with 
> putting characters into character ranges. Please file 
> https://issues.dlang.org/enter_bug.cgi
>
> -Steve


Thanks a lot for the clear explanation!
Issue has been created here: 
https://issues.dlang.org/show_bug.cgi?id=14998