result of atan is never more precise than double

3 results were exact to double the precision

20 largest ulp errors (stored in a double)
   0.50028 ulp for atan(-1.79850952600011849) = -1.06334607296139838)
   0.50024 ulp for atan(-0.231511231199999362) = -0.227503216980975198)
   0.50024 ulp for atan(-7.01694440599967262) = -1.42923735828428988)
   0.50022 ulp for atan(-4.36803014200022588) = -1.34573857399357166)
   0.50021 ulp for atan(-0.193720938600108777) = -0.191350775199167156)
   0.50020 ulp for atan(6.60531107599111689) = 1.42054399441825518)
   0.50020 ulp for atan(-0.273385260600019553) = -0.266864381664067341)
   0.50018 ulp for atan(-1.68497234999996448) = -1.03518359165182883)
   0.50016 ulp for atan(2.90196800600000637) = 1.23894587233259124)
   0.50016 ulp for atan(0.691743795200012945) = 0.605163368553421455)
   0.50015 ulp for atan(-0.500819921400074697) = -0.46430333097066423)
   0.50014 ulp for atan(-0.620286544600136325) = -0.555202681852450031)
   0.50014 ulp for atan(9.26453970399937532) = 1.46327416309335812)
   0.50013 ulp for atan(0.118152693199995815) = 0.117607446782601849)
   0.50013 ulp for atan(-0.758092139999913206) = -0.64865999416572695)
   0.50013 ulp for atan(0.810735118400030319) = 0.681252554619064865)
   0.50013 ulp for atan(5.25502219400538628) = 1.38275049106242154)
   0.50013 ulp for atan(-1.37842364999983524) = -0.943182511954652414)
   0.50012 ulp for atan(-0.273385260599956492) = -0.266864381664008721)
   0.50011 ulp for atan(0.788602522000052875) = 0.667752519803769484)

<tr><td align=left><a href=atan.res>atan</a></td><td align=right>870</td><td align=right>0.50028</td><td>-1.79850952600011849</td><td>-1.06334607296139838</td></tr>