what exactly is string length?

[mw]

On Friday, 2 April 2021 at 04:49:22 UTC, mw wrote:
> On Friday, 2 April 2021 at 04:43:48 UTC, rikki cattermole wrote:
>> On 02/04/2021 5:38 PM, mw wrote:
>>> On Friday, 2 April 2021 at 04:36:01 UTC, rikki cattermole 
>>> wrote:
>>>> On 02/04/2021 5:32 PM, mw wrote:
>>>>> ---
>>>>> import std;
>>>>> import std.conv : text;
>>>>>
>>>>>
>>>>> void main()
>>>>> {
>>>>>     char[6] s;
>>>>>     s = "abc";
>>>>>     writeln(s, s.length);  // abc6, ok it's the static 
>>>>> array's length
>>>>>
>>>>>     string t = text("head-", s, "-tail");
>>>>>     writeln(t, t.length);  // head-abc-tail16, why?
>>>> assert(t[9] == '\0');
>>>>> }
>>>>> ---
>>> 
>>> I don't get it, what do you mean by the assertion:
>>> 
>>> 
>>> assert(t[9] == '\0');
>>> 
>>> 
>>> t == "head-abc-tail"
>>
>> Not all characters can be printed such as NULL.
>>
>> [104, 101, 97, 100, 45, 97, 98, 99, 0, 0, 0, 45, 116, 97, 105, 
>> 108]
>
> So you mean inside the writeln() call, the 0s are skipped?
>
> Well, if I use `string t` as filename, it will try to looking 
> for a file called:
>
> "head-abc\0\0\0-tail" instead of just "head-abc-tail" ?
>
> or it's platform dependent?

Then how can I construct `t`? to make this assertion true:

     assert(t == "head-abc-tail");  // failed!