[fpc-pascal] math with infinity and NaN

[C Western]

On 20/06/18 21:58, Florian Klämpfl wrote:
> Am 19.06.2018 um 23:50 schrieb James Richters:
>> I’ve been updating my old programs to use the MATH unit in freepascal 
>> and while testing things I came across a runtime error 217  Invalid 
>> floating point operation.  Here is my test program
>>
>> Uses math;
>>
>> var
>>
>>     variable1:double;
>>
>>     variable2:double;
>>
>> Begin
>>
>> variable1:= Infinity;
>>
>> variable2:= -1*Infinity;
>>
>> Writeln(variable1,' ',Variable2,' ',Variable1+Variable2);
>>
>> End.
>>
>> My output is:
>>
>> Running "i:\programming\test\testmath.exe "
>>
>> An unhandled exception occurred at $004015F6:
>>
>> EInvalidOp: Invalid floating point operation
>>
>>    $004015F6  main,  line 8 of i:/programming/test/testmath.pas
>>
>>                      +Inf                     -Inf
>>
>> According to the link here: https://en.wikipedia.org/wiki/NaN
>>
>> NaN should be produced:
> 
> No. The invalid operation is not masked by default. If you do so, FPC 
> just write Nan.

My initial testing indicates that, even with exceptions masked, the 
exception was raised: (or am I using the wrong routine?)

Uses math;
var
     variable1:double;
     variable2:double;
Begin
SetExceptionMask([exDenormalized,exZeroDivide,exOverflow,exUnderflow,exPrecision]);
variable1:= Infinity;
variable2:= -1*Infinity;
Writeln(variable1,' ',Variable2,' ',Variable1+Variable2);
end.

./t
An unhandled exception occurred at $00000000004002A1:
EDivByZero: Division by zero
   $00000000004002A1  main,  line 9 of t.pas

                     +Inf                     -Inf

Colin