19 Apr
2012
19 Apr
'12
5:31 a.m.
On Wed, 18 Apr 2012 16:45:05 +0200, Brent Yorgey
On Tue, Apr 17, 2012 at 02:41:15PM -0700, Tim Perry wrote:
seq evaluates to Weak Head Normal Form (WHNF). WHNF is the first contructor. So your use of seq only evaluates the first number and the cons. I.E., it evaluates to: s:(Thunk)
Actually, it doesn't even force the first number. You just get
Thunk : Thunk
A nice way to demonstrate this, is the following GHCi session: Prelude> undefined `seq` print "OK" *** Exception: Prelude.undefined Prelude> [undefined] `seq` print "OK" "OK" Regards, Henk-Jan van Tuyl -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --