Chris,
Having said that, NaN is usually "safer" in that its use causes error,
>> making your bugs easier to spot.
>>
>
> agreed, I like NaN as a fill value, but there's a downside -- NaN dpes not
> equal NaN, so code that does:
>
> if something == fill_value:
>
> Will not work. It can be tricky.
>
That's exactly the reason for the "isnan()" function:
if (isnan(fill_value)) . . .
The Fortran language also includes such a function as part of its language
standard:
use:: ieee_arithmetic
if (ieee_is_nan(fill_value)) then
. . .
In addition, Fortran compilers tend to include a compile option to enable
"floating-point exception traps". If you enable the "invalid value" trap at
the compile time, at the runtime, the program stops with an error message
as soon as a NaN is generated or operated upon. This sometimes helps debug
your code.
Ryo
