Re: [Axiom-math] if-expression and variables

[Ralf Hemmecke]

Dear Stefan,

as others already have pointed out, for Axiom, your question is not 
really well posed.

In Axiom

  if x<10 then 2*x else 5*x^2

is *not* an expression (as you might know it from other untyped CAS like 
Mathematica or Maple), but rather a programming language construct. In 
other words, if Axiom sees this, it is evaluated. So the result is 
either 2*x or 5*x^2 depending on the (boolean) outcome of the evaluation 
of x<10.

I think, Bill suggested to use something like InputForm. There it would 
be possible to represent an if-expression unevaluated.

But you should rather say what you actually want (it's not the same what 
you expect).

In order for us to suggest you a proper way to handle your use case, you 
should tell us why you want a piecewise function and (more important) 
what you later want to do with that function.

Until we have that information, everything would be just digging in the 
dark.

Ralf

On 04/30/2011 08:40 PM, Stefan Karrmann wrote:
> Dear all,
>
> I'm new to axiom and have a problem with piecewise functions.
>
> test1 (x | x<  10) == 2*x
> test1 (x | x<  10) == 5*x^2
> test1
> ->
>     test1 (x | x<  10) == 2x
>     test1 (x | ^ x<  10) == 5x
>                                                     Type: FunctionCalled
> test1 y
> ->
>       2
>     5y
>
> I expected something like (if y<  10 then 2*y else 5*y**2).
>
> How is it possible to pass a Variable to a piecewise function respecting
> the pieces?
>
> PS: Using a block and =>  or explicit if-then-else does not help.