In the case statement for the half function I think variable m is bound to the value of (snd (half (n - 1)). With this assumption, I have have written a guarded version called half1. Is it always possible to write case statements as a set of conditional equations? My intuition is that this should be possible and that the guarded version reduces pattern matching? Thanks, Pat data EvenOdd = Even | Odd deriving (Show,Eq) half 0 = (Even,0) half n = case half (n-1) of (Even,m) -> (Odd,m) (Odd,m) -> (Even,m+1) half1 0 = (Even , 0) half1 n | (fst (half (n - 1)) == Even) = (Odd , (snd (half (n - 1)))) half1 n | (fst (half (n - 1)) == Odd) = (Even , ((snd (half (n - 1))) + 1)) -- This email originated from DIT. If you received this email in error, please delete it from your system. Please note that if you are not the named addressee, disclosing, copying, distributing or taking any action based on the contents of this email or attachments is prohibited. www.dit.ie Is ó ITBÁC a tháinig an ríomhphost seo. Má fuair tú an ríomhphost seo trí earráid, scrios de do chóras é le do thoil. Tabhair ar aird, mura tú an seolaí ainmnithe, go bhfuil dianchosc ar aon nochtadh, aon chóipeáil, aon dáileadh nó ar aon ghníomh a dhéanfar bunaithe ar an ábhar atá sa ríomhphost nó sna hiatáin seo. www.dit.ie Tá ITBÁC ag aistriú go Gráinseach Ghormáin – DIT is on the move to Grangegorman http://www.dit.ie/grangegorman