I'm afraid it doesn't seem to be quite right yet :-( Consider instance Foo Maybe where foo = 5 => {4}instance Foo Maybe where {4}foo = 5 => {instance Foo Maybe where {}}foo = 5 The second {4} has meant there is no <4> to cause an implicit semicolon to be inserted. This can be fixed by changing L ({n}:ts) (m:ms) = { : (L ts (n:m:ms)) if n > m, (Note 1) = { : } : (L ts (m:ms)) otherwise to L ({n}:ts) (m:ms) = { : (L ts (n:m:ms)) if n > m, (Note 1) = { : } : (L (<n>:ts) (m:ms)) otherwise Thanks Ian, having a bad day, predominantly due to the layout rule :-(