2009/6/17 Robert Bradshaw <rober...@math.washington.edu>:
>
> On Jun 17, 2009, at 3:05 AM, Utpal Sarkar wrote:
>
>> Thanks for the replies.
>> I noticed something funny: if you call x = var("X") in some scope, it
>> is X that is injected into the global scope, not x. In fact I thought
>> that the argument was merely a print name.
>
> var("X") is what makes the variable, there's nothing special about
> assignment. For example, if I wrote
>
> sage: x = var("X") + 1
>
> then x would have the value X + 1, and as a side effect, X would be
> injected into the global scope. This seems like a surprising artifact
> to many people, and is certainly not like anything Python does. Was
> there a strong justification for doing this?
If I remember correctly:
1. The symbolic calculus code is not aimed at experience Python
programmers or users.
2. It is very nice for var('x,y,z,theta') to work, and to not require
the user to type:
x,y,z,theta = var('x,y,z,theta')
3. Having var at all is a compromise -- many symbolic calculus users
would prefer for undefined vars to just "magically" be defined, as is
done in Mathematica, Maple, Maxima, Axiom (?), etc.
-- William
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