include "NSLog.incl"

double local fn Square( d as double )
end fn = d * d

double local fn AverageSquareDiff( d as double, predictions as CFArrayRef )
  double sum = 0.0
  for CFNumberRef num in predictions
    sum += fn Square( fn NumberDoubleValue( num ) - d )
  next
  return sum / fn ArrayCount( predictions )
end fn = 0.0

CFStringRef local fn DiversityTheorem( truth as double, predictions as CFArrayRef )
  double average = fn NumberDoubleValue( fn ObjectValueForKeyPath( predictions, @"@avg.self" ) )
  CFStringRef    avgErr = fn StringWithFormat( @"%4.5f", fn AverageSquareDiff( truth, predictions ) )
  CFStringRef  crowdErr = fn StringWithFormat( @"%6.5f", fn Square( truth - average ) )
  CFStringRef diversity = fn StringWithFormat( @"%6.5f", fn AverageSquareDiff( average, predictions ) )
  return fn StringWithFormat( @"Average error : %@\nCrowd error   : %@\nDiversity     : %@\n", avgErr, crowdErr, diversity )
end fn = NULL

NSLog( @"Diversity prediction with crowd estimates of 48, 47 and 51:" )
NSLog( @"%@\n", fn DiversityTheorem( 49.0, @[@48.0, @47.0, @51.0] ) )

NSLog( @"Diversity prediction with crowd estimates of 48, 47, 51 and 42:" )
NSLog( @"%@\n", fn DiversityTheorem( 49.0, @[@48.0, @47.0, @51.0, @42.0] ) )

HandleEvents