Nothrow, pure in druntime

[Michel Fortin]

On 2009-01-26 14:21:18 -0500, Walter Bright <newshound1 at digitalmars.com> said:

>> I guess it's reasonable to argue that using the floating-point flags is 
>> sufficiently hard-core that pure and nothrow should pretend that they 
>> don't exist.
>> 
>> Still, some functions (especially correctly-rounded floating-point i/o) 
>> go to a lot of trouble to support them.  I have a suspicion that it's 
>> not worth the effort.
> 
> So we have two options. One is to say that floating point arithmetic 
> cannot be made pure. The other is to ignore the problem (saying it's 
> undefined behavior).

I see another: the compiler keeps track of the state of floating point 
flags inside a function, and prevent pure optimisations across those 
boundaries. Of course, the language would have to expose a mean to 
change these flags in order for it to work... and prevent any such 
change from leaking after the lifetime of a function.

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/