const and phobos string functions

[Regan Heath]

I wanted to post this real/concrete case of where 'const' and the 
current phobos implementation of certain string routines combine to 
cause a few irritations, inefficiencies and some IMO illogical behaviour.

Note in the code below 'remove' is a template function which uses 
'memmove' to remove an item from the array.

(The code):

char[][] tmp;

tmp = cast(char[][])splitlines(cast(string)read(a[3..$]));
foreach(ref line; tmp) line = cast(char[])strip(line);
for(int i = 0; i < tmp.length; i++)
{
   if (tmp[i].length == 0)
     tmp.remove(i);
}

(The problem):

Notice all the cast()'s required above.  I am of the belief that casting 
should only be done in exceptional circumstances, and this shouldn't be 
one of them.

If you consider char[] as being a a string which you are the full owner 
of, you can change it at will, and 'string' as being a string which you 
are not the full owner of, as you can only read it then in many cases it 
doesn't make sense to pass a char[] to a function and get a 'string' 
back, unless the function has 'taken ownership' of the string data or is 
returning different string data which you are not the owner of.

The obvious case where it make sense is a property setter which might 
copy the input and return a 'string' reference to the copy.

In the cases above (splitlines, strip) it doesn't make sense for the 
function to 'take ownership' of the strings as they do not store them 
beyond the lifetime of the function call.

Therefore if passed a char[] they should return char[][] and char[] 
respectively.

Of course if passed 'string' they should return 'string[]' and 'string' 
respectively.

(The solution):

Given the requirements it seems templating is the obvious solution.  I 
have described in earlier posts (though these relate to tolower 
specifically):

http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=55335
http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=55337

All the phobos routines should likely be templated in the same fashion.

Regan