reddit.com: first Chapter of TDPL available for free

[Jarrett Billingsley]

On Sat, Aug 8, 2009 at 8:44 PM, Jos van Uden<jvu at nospam.nl> wrote:
> Andrei Alexandrescu wrote:
>>
>>
>> http://www.reddit.com/r/programming/comments/975ng/diving_into_the_d_programming_language_tdpl/
>>
>> (Don't tell anyone, but I plan to rewrite it.)
>>
>> Andrei
>
> Is this supposed to compile? I keep getting error messages.
>
> import std.stdio, std.string;
>
> void main() {
>   uint[string] dic;
>   foreach (line; stdin.byLine) {
>      // Break sentence into words
>      string[] words = split(strip(line));
>      // Add each word in the sentence to the vocabulary
>      foreach (word; words) {
>         if (word in dic) continue; // nothing to do
>         uint newID = dic.length;
>         dic[word] = newID;
>         writeln(newID, '\t', word);
>      }
>   }
> }
>
>
> test.d(7): Error: function std.string.split (immutable(char)[] s) does not
> match parameter types (char[])
> test.d(7): Error: cannot implicitly convert expression (strip(line)) of type
> char[] to immutable(char)[]
> test.d(7): Error: expected 2 function arguments, not 1
>
>
> I've changed the code to:
>
> import std.stdio;
> import std.string;
>
> void main() {
>
>    uint[string] dic;
>    foreach (line; stdin.byLine) {
>        string[] words = split(strip!(string)(line));
>        foreach (word; words) {
>            if (word in dic) {
>                continue;
>            }
>            uint newID = dic.length;
>            dic[word] = newID;
>            writeln(newID, '\t', word);
>        }
>    }
> }
>
> but I still get an error...
>
> test.d(12): Error: cannot implicitly convert expression (line) of type
> char[] to immutable(char)[]
>

It's not documented, but the .byLine method returns char[], not
immutable(char)[] (string).  This is because the 'line' variable is
reused on each new line of the input, to improve speed.  I think to
solved this, you should use:

auto words = split(strip(line.idup));

The .idup creates a new duplicate of the line that is immutable.

Now, why split() doesn't take a const(char)[] is beyond me..