{-|
    Probability of True is @n/m@.  Precondition: @0<n<m@    
-}
arbitraryBoolRatio :: Int {-^ @n@ -} -> Int {-^ @m@ -} -> Gen Bool 
arbitraryBoolRatio n m | 0 < n && n < m =
    frequency [(n, return True), (m - n, return False)]
arbitraryBoolRatio :: Int {-^ @n@ -} -> Int {-^ @m@ -} -> Gen Bool
arbitraryBoolRatio n m | 0 < n && n < m =
    frequency [(n, return True), (m - n, return False)]
arbitraryBoolRatio n m | 0 < n && n < m =
    frequency [(n, return True), (m - n, return False)]