Ralf Hemmecke <[email protected]> writes:
| On 03/12/2012 05:51 PM, Serge D. Mechveliani wrote:
| > I need to build (in Spad) an element x : (D : EuclideanDomain)
| > into SExpression.
|
| The first question I would have: Why?
| SExpression is losing all type information, as a FriCAS programmer,
| one would think twice about the need of such a function.
|
| I D is a EuclideanDomain, then there are no exported functions to turn
| an element of D into SExpression. If you don't additionally require
| from D that it exports a function foo: % -> SExpression, the only
| thing you can do, is via (type unsafe) tricks.
OpenAxiom allows users to *safely* unpack values of the existential type Any:
case expr is
x: exist(D: EuclideanDomain) . D => something with x
otherwise => do something else
See:
http://sourceforge.net/apps/trac/open-axiom/browser/1.4.x/src/algebra/any.spad.pamphlet#L184
http://sourceforge.net/apps/trac/open-axiom/browser/1.4.x/src/algebra/any.spad.pamphlet#L188
-- Gaby
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