Dylan Thurston <dpt@math.harvard.edu> writes

In thinking about various issues with the numeric classes, I came up with the following question: Is there a problem with having a class 'Convertible' as follows?

class Convertible a b where convert :: a -> b

[..]

The basic algebra library BAL http://www.botik.ru/pub/local/Mechveliani/basAlgPropos/bal-pre-0.01/ suggests class Cast a b where cast :: a -> b -> a If s is an element of a certain domain, then one can use the construction cast s x to convert various data x to corresponding canonical values in the domain defined by s. For example, if s <- Z[x] is a polynomial over Integer, then the expressions cast s 2, cast s (2,3) give the constant 2, considered as a polynomial, and a one-term polynomial equal to 2*x^3. Also BAL overloades +, * ... by hiding-reexporting the standard Prelude and implements the algebraic categories Group, Ring ... ----------------- Serge Mechveliani mechvel@botik.ru