• Dart

if (r1.isNaN) {
  print("This is a quiet NaN.");
} else {
  print("This is a number.");
}

• Fortran

  character (len=:), allocatable :: msg
  if (ieee_support_nan(r1)) then
     if (ieee_class(r1) == ieee_quiet_nan) then
        msg = "This s a quiet NaN."
     else if (ieee_class(r1) == ieee_signaling_nan) then
        msg = "This is a signaling NaN."
     else
        msg = "This is a number."
     end if
  else
     msg = "NaNs are not supported."
  end if
  write (*,'(A)') msg

• Java

if (isNaN(r1)) out.println("This s a quiet NaN.");
else out.println("This is a number.");

• Java

if (r1 != r1) out.println("This s a quiet NaN.");
else out.println("This is a number.");

• Pascal

  if r1.IsNan then
  begin
   if (TDoubleRec(r1).Data and $4000000000000000) = $4000000000000000 then
     writeln('This is a quiet NaN')
   else
     writeln('This is a signalling NaN');
  end
  else
    writeln('This is a number: ',r1);

• Perl

my @r = (nan, nan, 1.234);

setpayloadsig $r[1],'999';

foreach my $r1 ( @r ) {
    if ( isnan $r1 ) {
        printf "This is a %s NaN\n",
            issignaling($r1) ? 'signaling' : 'quiet';
    } else {
        printf "This is not a NaN: %s\n", $r1;
    }
}

# Output:
# This is a quiet NaN
# This is a signaling NaN
# This is not a NaN: 1.234

• Python

if math.isnan(r1):
    print('This is a quiet NaN.')
else:
    print('This is a number.')

• Python

d = Decimal(r1)
if d.is_snan(): print('This is a signaling NaN.')
if d.is_qnan(): print('This s a quiet NaN.')
if not d.is_nan(): print('This is a number.')