problem with byLine

[dcoder]

On Monday, 14 May 2012 at 09:00:14 UTC, simendsjo wrote:
> On Mon, 14 May 2012 10:41:54 +0200, Christian Köstlin 
> <christian.koestlin at gmail.com> wrote:
>
>> Hi,
>>
>> i wanted to output an ascii-file line by line, but reversed.
>> the idea was to open the file, use byLine to read it 
>> line-by-line, make this range an array, and retro this array.
>>
>> But when i convert byLine to an array, the result is already 
>> trash.
>>
>> Please see this snippet.
>>
>> import std.stdio;
>> import std.array;
>>
>> int main(string[] args) {
>>   if (args.length != 2) {
>>     throw new Exception("Usage: " ~ args[0] ~ " file1");
>>   }
>>
>>   auto f = File(args[1], "r");
>>   auto i = array(f.byLine());
>>   foreach (l; i) {
>>     writeln(l);
>>   }
>>   return 0;
>> }
>>
>> Any idea why this happens?
>>
>> regards
>>
>> christian köstlin
>
> I believe byLine reuses the internal buffer. Try duping the 
> lines:



>   auto i = f.byLine().map!"a.idup"().array();


Can someone please explain to me the last line?

I'm trying to learn D, by playing with code and reading this 
forum.  I'm a slow learner.  :)

Anyways, I looked at std.stdio code and noticed that byLine 
resturns a struct ByLine, but where does the .map come from?  
Thanks!