char[][] join ==> string

[spir]

On 04/07/2011 09:52 AM, spir wrote:
> On 04/07/2011 03:07 AM, Ali Çehreli wrote:
>>> Given an array of strings std.string.join() returns a single string:
>>>
>>> import std.string;
>>> void main() {
>>> string[] a1 = ["hello", "red"];
>>> string j1 = join(a1, " "); // OK
>>> }
>>>
>>>
>>> But in a program I need an array of mutable arrays of chars. If I join the
>> arrays I get a mutable array of chars.
>> [...]
>> Finally, casting ourselves works:
>>
>> string j2 = cast(string)join(a2, " ");
>
> Oh, that's very good news! Thans Ali, I never thought at that solution. I'm
> often i/dup-ing from/to string to manipulate text due to the fact there is no
> automatic conversion.
> cast() works in place, doesn't it? so this is supposed avoid to avoid copy.
>
> PS: Checked: indeed, it works in-place. But watch the gotcha:
>
> unittest {
> string s = "abc";
> char[] chars = cast(char[])s;
> chars ~= "de";
> s = cast(string) chars;
> writeln(s, ' ', chars); // abcde abcde

Sorry: forgot this line:
     assert(s.ptr == chars.ptr);	// pass

>
> chars[1] = 'z';
> writeln(s, ' ', chars); // azcde azcde
> }
>
> s's chars are mutable ;-) So, I guess there is /really/ no reason for implicite
> casts between char[] and string no to exist. (I assumed the reason was
> precisely to avoid such traps).
>
> Denis

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