Re: Calculating/Averaging over a struct value

[Jesse Phillips]

On Wednesday, 21 March 2012 at 17:02:05 UTC, Brian Brady wrote:
As per the commented section, I want to be able to dynamically 
figure out,
which member of the struct to average across, for all the 
structs in the array.

Timon has given you an good example to get D to generate some 
code for you. I would also point out that combining your if block 
or even Timon's solution with a template:

double average(string param)(Data[] x)
{
 static if (!isNumeric!(typeof(mixin("Data."~param))))
   return -1;
 else
 {
  //auto average = reduce!("a."~param~" + b."~param)(x)/x.length;
  typeof(return) average = 0;
  foreach(v; x) {
          mixin("average += v."~param~";");
  }
  return average/x.length;
 }
}

Note, I commented out reduce as it uses the array type instead of 
the calculation type. I think I'll file than as a bug. Also the 
reduce version would not give you a double back even if it did 
work, need a cast in there.

Now calculating the parameter is just

auto ans = average!"d1"(x);