floating point - nan initializers

[Sean Kelly]

Sean Kelly wrote:
> Sean Kelly wrote:
>> John Stoneham wrote:
>>> Walter Bright wrote:
>>>> I've also heard from people who do serious numerical work that, at 
>>>> last, D is a language that cares about numerical analysis and its 
>>>> needs. Default initializing to nan is part of that - it forces the 
>>>> user to *think* about what he wants the initial value to be. 
>>>> Initializing it by default to 0 means that it can easilly be 
>>>> overlooked, and 0.0 can introduce undetected, subtle errors in the 
>>>> result.
>>>>
>>>
>>> I agree. I'm currently working on an involved combinatorial 
>>> calculation, and having one of the doubles auto-initialized to NAN 
>>> help me find a bug in one of the calculations which would have been 
>>> very difficult to find otherwise.
>>>
>>> I say keep it.
>>>
>>>
>>>> There is a 'nan' value for pointers - null, a 'nan' value for UTF-8 
>>>> chars - 0xFF - which is an illegal UTF-8 character. If there was a 
>>>> 'nan' value for ints, D would use it as the default, too.
>>>>
>>>
>>> There *is* a way get this behavior, and it can be done at compile 
>>> time: raise an error when an int is assigned an initial value which 
>>> cannot be calculated at compile time. This behavior could even be 
>>> turned on with a command-line switch, -nan, or whatever.
>>
>> This would be nice.
> 
> I take it back:
> 
> struct S { int i; }

Actually, does this work?

struct S { int i = 5; }

Not quite a flexible as a ctor, but it would be sufficient for the above 
suggestion.

Sean