[J3] branch based on ieee class ?

[Bill Long]

I tried Vipul’s example code with all 4 compilers I have, and every one compiles it with no error and executes as expected. 

It seems your main problem is a poor choice of compiler. 

Cheers,
Bill


> On Nov 7, 2019, at 10:46 AM, Dan Nagle via J3 <j3 at mailman.j3-fortran.org> wrote:
> 
> Hi,
> 
> Yes, I didn't read far enough.
> 
> But neither of the compilers I'm targeting support == and /=  :-(
> 
> 
>> On Nov 7, 2019, at 09:42 , Vipul Parekh via J3 <j3 at mailman.j3-fortran.org> wrote:
>> 
>> Hello Dan,
>> 
>> See section 17.2 Derived types, constants, and operators defined in
>> the modules in 18-007r1.pdf, p3 on IEEE_ARITHMETIC module,
>> particularly lines 27 thru' 30 which state,
>> 
>> 27 * The pure elemental operator == for two values of one of these
>> types to return true if the values are the
>> 28   same and false otherwise.
>> 29 * The pure elemental operator /= for two values of one of these
>> types to return true if the values differ and
>> 30   false otherwise.
>> 
>> From what I understand, you will have to construct your case using
>> either of the above-mentioned operators e.g.,
>> 
>>  use, intrinsic :: ieee_arithmetic, only : ieee_class,
>> ieee_negative_normal, operator(==)
>>  real :: x
>>  x = -1.0
>>  if ( ieee_class(x) == ieee_negative_normal ) then
>>     print *, "x is IEEE_NEGATIVE_NORMAL"
>>  else
>>     print *, "The IEEE class of x is not as expected!"
>>  end if
>> end
>> 
>> Upon execution, the program output is expected as:
>> x is IEEE_NEGATIVE_NORMAL
>> 
>> Regards,
>> Vipul Parekh
>> 
>> On Thu, Nov 7, 2019 at 10:38 AM Dan Nagle via J3
>> <j3 at mailman.j3-fortran.org> wrote:
>>> 
>>> Hi,
>>> 
>>> How to?
>>> 
>>> C1145 removes the select case option (my first choice), and
>>> Table 10.2 eliminates if-blocks by not listing ieee_class_type
>>> among the allowed operands for == and /= (or .eqv. and .neqv.).
>>> 
>>> I'm writing a workshop on ieee 754 and I would like to write
>>> a diagnostic routine that can print "this is an X" where
>>> X is one of the ieee_class_type values.  So I want to branch
>>> to select the correct label per class.
>>> 
>>> (With the select case, a range of values does not seem to make sense.
>>> But I want to case each one singly, so that's no matter to the task at hand.)
>>> 
>>> 
>>> --
>>> 
>>> Cheers!
>>> Dan Nagle
>>> 
>>> 
> 
> 
> --
> 
> Cheers!
> Dan Nagle
> 
> 

Bill Long                                                                       longb at cray.com
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