Library report examples

[Ian Lynagh]

Hi guys,

The library report defines

  -- Diagonal of a square matrix
  diag :: (Ix a) => Array (a,a) b -> Array a b
  diag x = ixmap (l,u) (\i->(i,i)) x
   where ((l,l'),(u,u')) | l == l' && u == u'  = bounds x

but ghc, hugs and nhc98 all loop (trying to get and test the value of l
I believe).


I am also curious why, for example,

  row :: (Ix a, Ix b) => a -> Array (a,b) c -> Array b c
  row i x = ixmap (l',u') (\j->(i,j)) x where ((l,l'),(u,u')) = bounds x

isn't written as

  row :: (Ix a, Ix b) => a -> Array (a,b) c -> Array b c
  row i x = ixmap (l,u) (\j->(i,j)) x where ((_,l),(_,u)) = bounds x
                   ~~~                        ~~~   ~~~


Thanks
Ian