Proposal: fixing the 'pure' floating point problem.

[Don]

Walter Bright wrote:
> Don wrote:
>> That's true, but if you're in a floatingpoint module, and you call a 
>> non-floatingpoint module, it's your responsibility to make sure that 
>> the rounding mode is back to normal. You're saying that you don't care 
>> about the status flags. So it's your own fault if you get surprising 
>> results.
>>
>> The primary use for adjusting the rounding mode is for things like 
>> implementing interval arithmetic. Thus, it's only ever used for small 
>> functions.
> 
> Perhaps we can go with something simpler. If you call a pure function, 
> then the modes must be set to their defaults.

But then nothing in std.math can be pure.