A Philosophy of Software Design

[Walter Bright]

On 6/27/2026 5:13 PM, Forum User wrote:
> On Saturday, 27 June 2026 at 19:48:44 UTC, Walter Bright wrote:
>> [...]
>> It behaves much like the floating point NaN value, which is a generally 
>> misunderstood and underappreciated.
> 
> NaNs increase hidden complexity and require more source code
> (i.e. increase source code complexity) in order to do things right:
> 
>     auto t = (t2);
>     if (t < 2.0)
>        writeln ("met the climate target");
>     else
>        writeln ("failed to meet the climate target");

The reader would want to know how well the number met the target, or how badly 
it failed:

```d
if (t < 2.0)
      writeln ("%g met the climate target", t);
else
     writeln ("%g failed to meet the climate target", t);
```

Besides, getting a NaN result is always better than getting an arbitrary number 
with no clue whether it is valid or a bug.