# Concerning Time.TimeDiff

**Keith Wansbrough
**
Keith.Wansbrough@cl.cam.ac.uk

*Thu, 19 Jun 2003 17:04:37 +0100*

Alistair Reid writes:
>* I suspect Integer could be optimized (by recognizing that most uses of Integer
*>* are for values that fit in 31 bits) so that the difference is pretty minimal.
*>* but this would have limited effect on a date like 19 June 2003 which is (very
*>* roughly) 2^69 picoseconds since the epoch.
*
It *is* optimised on GHC: libraries/base/GHC/Num.lhs says
-- | Arbitrary-precision integers.
data Integer
= S# Int# -- small integers
#ifndef ILX
| J# Int# ByteArray# -- large integers
#else
| J# Void BigInteger -- .NET big ints
foreign type dotnet "BigInteger" BigInteger
#endif
This doesn't change your basic point, though, that two Int64s will
probably be faster than one Integer.
--KW 8-)