use strict;
use warnings;

my @constraints = (
          {mid => 20, sd => 15},
          {mid => 30, sd => 25},
          {mid => 50, sd => 10},
     );

my $sum;

for my $cnst (@constraints) {
     my $value = RandFlat ($cnst->{mid}, $cnst->{sd});
     $cnst->{value} = $value;
     $sum += $value;
}

#scale so that percentages add up to 100
# this may push parameters outside bounds!

my $scale = 100.0 / $sum;
for my $cnst (@constraints) {
     my ($mid, $sd, $value) = @{$cnst}{'mid', 'sd', 'value'};
     
     $value = $value * $scale;
     printf "%5.1f +-%5.1f: %5.1f", $mid, $sd, $value;
     print " - bad" if ($value < ($mid - $sd)) || ($value > ($mid + $sd));
     print "\n";
}


sub RandFlat {
    #Return a rand () value with a flat distribution about the $mean +- $stdDev
    my ($mean, $stdDev) = @_;
    my $range = 2.0 * $stdDev;
    my $value = rand ($range);
    return $value + ($mean-$stdDev);
}

##</code><code>##

 20.0 +- 15.0:  22.7
 30.0 +- 25.0:  40.1
 50.0 +- 10.0:  37.2 - bad