On 12/24/2012 05:05 AM, Grigory Sarnitsky wrote:
> And what if I have Expression(Integer) ? Say,
> 
> (5) -> (sin x + y)^3 / ((sin x)^2 + (sin x + z)^3) 

By now I should be known on this mailing list as the person who doesn't
like Expression(Integer). Seemingly, everyone thinks that an element of
type Expression(Integer) is the same as an expression in Mathematica or
Maple. No, it is not!

In FriCAS, Expression(Integer) is represented as a rational function
where the variables are "kernels". Look deeper into the representation.

https://github.com/hemmecke/fricas-svn/blob/master/src/algebra/expr.spad.pamphlet#L113

That's the standard representation with all its consequences. If you
want something else, you need something else, not Expression(Integer).

What in other CAS is done by a simplify function (with unclear
semantics) is actually not existent in FriCAS. In FriCAS an element
(expression) x of type X is always turned into whatever the type X
thinks is appropriate. If you want x to show differently, you'd usually
have to coerce it into an appropriate type.

Look for example at this, maybe it gives you an idea how things would
have to be done. The trick is to make your types more specific, not the
"all including" Expression(Integer).

Since you haven't made exactly clear what you actually want to achieve
and whether you could perhaps temporarily work with a symbol sx instead
of the kernel sin(x), I'm unable to help any further.

Ralf


(3) -> a:=(2+%i)/(3+x+%i)

          2 + %i
   (3)  ----------
        x + 3 + %i
        Type: Fraction(Polynomial(Complex(Integer)))
(4) -> a::Complex(Fraction Polynomial Integer)

           2x + 7          x + 1
   (4)  ------------ + ------------ %i
         2              2
        x  + 6x + 10   x  + 6x + 10
        Type: Complex(Fraction(Polynomial(Integer)))

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