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Programming-Idioms

  • Python
  • Smalltalk
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  • D

Idiom #270 Test for quiet or signaling NaN

Given a floating point number r1 classify it as follows:
If it is a signaling NaN, print "This is a signaling NaN."
If it is a quiet NaN, print "This s a quiet NaN."
If it is not a NaN, print "This is a number."

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

Python makes no effort to distinguish signaling NaNs from quiet NaNs, and behavior for signaling NaNs remains unspecified. Typical behavior is to treat all NaNs as though they were quiet.
from decimal import Decimal
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.')
if (r1.isNaN) {
  print("This is a quiet NaN.");
} else {
  print("This is a number.");
}

Dart has no concept of signaling NaN. NaN are all quiet AFAIK.
New implementation...
< > ⌨
tkoenig 
if math.isnan(r1):
    print('This is a quiet NaN.')
else:
    print('This is a number.')

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.')
if (r1.isNaN) {
  print("This is a quiet NaN.");
} else {
  print("This is a number.");
}
  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
if (isNaN(r1)) out.println("This s a quiet NaN.");
else out.println("This is a number.");
if (r1 != r1) out.println("This s a quiet NaN.");
else out.println("This is a number.");
  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);

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