• Andrej Mitrovic <andrej.mitrovich gmail.com> Sep 02 2011
• Timon Gehr <timon.gehr gmx.ch> Sep 02 2011
• David Nadlinger <see klickverbot.at> Sep 02 2011
• David Nadlinger <see klickverbot.at> Sep 02 2011
• David Nadlinger <see klickverbot.at> Sep 02 2011
• "Vladimir Panteleev" <vladimir thecybershadow.net> Sep 02 2011
• Andrej Mitrovic <andrej.mitrovich gmail.com> Sep 02 2011

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

string[2][] results;
results ~= ["foo", ""];
results ~= ["foobar", ""];

size_t len;
foreach (res; results)
{
    len = max(len, res[0].length);
}

That gives me '6'. I want to convert this to functional-style code
with reduce. I've tried:

len = reduce!(max!"a[0].length")(results);

That's not it. Any clues?

Timon Gehr <timon.gehr gmx.ch> writes:

On 09/02/2011 07:11 PM, Andrej Mitrovic wrote:
 string[2][] results;
 results ~= ["foo", ""];
 results ~= ["foobar", ""];

 size_t len;
 foreach (res; results)
 {
      len = max(len, res[0].length);
 }

 That gives me '6'. I want to convert this to functional-style code
 with reduce. I've tried:

 len = reduce!(max!"a[0].length")(results);

 That's not it. Any clues?



len = reduce!max(map!"a[0].length"(results));

David Nadlinger <see klickverbot.at> writes:

On 9/2/11 7:11 PM, Andrej Mitrovic wrote:
 string[2][] results;
 results ~= ["foo", ""];
 results ~= ["foobar", ""];

 size_t len;
 foreach (res; results)
 {
      len = max(len, res[0].length);
 }

 That gives me '6'. I want to convert this to functional-style code
 with reduce. I've tried:

 len = reduce!(max!"a[0].length")(results);

 That's not it. Any clues?


The return type of the function/… passed to reduce must be the same as 
its argument type, because reduce is really just another way to express 
the above loop.

In this case, you might want to combine map and reduce:
reduce!max(map!"a[0].length"(results))

David

David Nadlinger <see klickverbot.at> writes:

On 9/2/11 7:23 PM, David Nadlinger wrote:
 […]  because reduce is really just another way to express
 the above loop.


On second thought: The one-argument overload of it, that is. You can 
also use differing types if you explicitly specify the starting value. 
For your example you could do something like:
reduce!"max(a, b[0].length)"(0, …).

David

David Nadlinger <see klickverbot.at> writes:

On 9/2/11 8:05 PM, David Nadlinger wrote:
 On 9/2/11 7:23 PM, David Nadlinger wrote:
 […] because reduce is really just another way to express
 the above loop.


 On second thought: The one-argument overload of it, that is. You can
 also use differing types if you explicitly specify the starting value.
 For your example you could do something like:
 reduce!"max(a, b[0].length)"(0, …).

 David


… as Vladimir already posted. Gah, I should really refresh d.D.learn 
before posting, it's quite impressive how fast simple questions are 
often answered here…

David

"Vladimir Panteleev" <vladimir thecybershadow.net> writes:

On Fri, 02 Sep 2011 20:11:38 +0300, Andrej Mitrovic  
<andrej.mitrovich gmail.com> wrote:

 string[2][] results;
 results ~= ["foo", ""];
 results ~= ["foobar", ""];

 size_t len;
 foreach (res; results)
 {
     len = max(len, res[0].length);
 }

 That gives me '6'. I want to convert this to functional-style code
 with reduce. I've tried:

 len = reduce!(max!"a[0].length")(results);

 That's not it. Any clues?


Here's another way which doesn't use map:

len = reduce!`max(a, b[0].length)`(0, results);

-- 
Best regards,
  Vladimir                            mailto:vladimir thecybershadow.net

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

Thanks guys!