IndexedMatrix.hs

   1 module IndexedMatrix where
   2 import Data.Set (Set)
   3 import qualified Data.Set as Set
   4 import Numeric.Matrix (Matrix, MatrixElement)
   5 import qualified Numeric.Matrix as Matrix
   6
   7 data IndexedMatrix r c e = IndexedMatrix
   8   { rowIndices    :: Set r
   9   , columnIndices :: Set c
  10   , stripIndices  :: Matrix e
  11   } deriving Show
  12
  13 indexedMatrix :: MatrixElement e =>
  14   Set r -> Set c -> (r -> c -> e) -> IndexedMatrix r c e
  15 indexedMatrix rs cs f = IndexedMatrix
  16   { rowIndices    = rs
  17   , columnIndices = cs
  18   , stripIndices  = Matrix.matrix (Set.size rs, Set.size cs) $ \(i, j) ->
  19       f (Set.elemAt (i - 1) rs) $ Set.elemAt (j - 1) cs
  20   }
  21
  22 firstMinorMatrix :: (Ord r, Ord c, MatrixElement e) =>
  23   IndexedMatrix r c e -> r -> c -> Maybe (IndexedMatrix r c e)
  24 firstMinorMatrix m r c =
  25   let
  26     rs = rowIndices m
  27     cs = columnIndices m
  28   in
  29   if (Set.member r rs && Set.member c cs)
  30   then Just $ IndexedMatrix
  31     { rowIndices    = Set.delete r rs
  32     , columnIndices = Set.delete c cs
  33     , stripIndices  = Matrix.minorMatrix (stripIndices m)
  34         (Set.findIndex r rs + 1, Set.findIndex c cs + 1)
  35     }
  36   else Nothing
  37