bugs in Time.hs

[Ross Paterson]

On Tue, Aug 26, 2003 at 05:53:32PM +0200, Härmel Nestra wrote:
> I found several divergences of the module  Time  of Hugs (v. Nov 
> 2002 for Linux) from the Haskell Report which can't be found neither
> in the list of known Hugs bugs nor in the list of differences from 
> Haskell 98 (the latter is also too old and claims that  Time  is not 
> yet available).

Thanks for the bug report.

> 1. The report specifies that the field  ctSec  of datatype 
> CalendarTime  must be exported outside the module. In Hugs, this field 
> is missing from the exports list.

This is already fixed in the development version, which uses the same
Time module as GHC.

> 2. The report requires (see the end of the penultimate paragraph 
> before the library starts) that " toClockTime l  converts  l  [...] 
> ignoring the contents of the  ctWDay ,  ctYDay ,  ctTZName ,  and  
> ctIsDST  fields". Hugs, however, does not ignore  ctIsDST .

It is wierd: it constructs an argument using ctIsDST, and then the
primitive evaluates that argument but ignores its value.  I'll remove
the argument from the primitive.

> 3. Additionally, the behaviour of the function  diffClockTime  is 
> strange in Hugs. In the returned record, at most two fields are 
> non-zero:  tdSec  and  tdPicosec . Thereby,  tdSec  is of type  Int  
> which leads to incorrect value in the case of big time differences. 
> The report is amazingly tongue-tied at this point, so it is even 
> difficult to argue that your implementation is diverging. It seems 
> natural to think however that this behaviour is not what was expected. 

Unfortunately this (tdSec::Int) is a known bug in the Haskell 98 Report,
which we must slavishly follow.

> 4. There seem to be problems with dates before year 1970.

That sounds like a Posix problem.