How to prevent evaluation.



Richard Hennessy wrote:
>
>      
>     It seems like in the %if function both the then part and the else
>     part are always expanded even when only one needs to be evaluated.
>
Maybe you could review what it is that %if does, and see if it is 
consistent with the semantics of %if to evaluate only one part?
I expect that it is not. But I've forgotten how %if is supposed to work 
and it isn't in the documentation I have.


>       Is there a way to stop evaluation of both parts
>

Certainly, but then it would be a different facility. Which do you 
want?  Also, Maxima generally is incapable of
avoiding a calculation because it might take too long. It can, of 
course, stop a calculation  after it has taken a while.
But not usually anticipating...