On Saturday, 16 April 2022 at 05:37:16 UTC-7 list...@gmail.com wrote:
>
> Thanks Samuel and Emmanuel.
>
> Follow up question: Why does
> var('lambda',n=1)
> fail?
>
Because the code in question tests the string actually passed in for
whether it's a valid python identifier.
Probably this is because the "n" optional argument was only added later.
However, there's been quite a discussion on what the appropriate binding
behaviour should be. One option would be to bind the actual returned result
(a tuple of the constructed symbols) to a name in the current namespace.
i.e., the result of
x = SR.var('x',n=3)
For that behaviour, the passed-in name would have to be a valid identifier.
So to future-proof sage, perhaps it's better to have this stricter check.
You can create symbols without the check: SR.symbol('lambda') works just
fine. To create the symbols you'd like, you can do:
L = (SR.symbol("lambda{}".format(i)) for i in range(3))
binding them to corresponding symbols would require a little more work .
It's basically
for c in L:
globals()[str(c)] = c
which works when typed in as-is, but requires some more trickery if it is
wrapped in a function in some module, due to the semantics of the actual
"globals()" call in python.
[in general, for anything other than direct interactive use, you should
probably not rely on binding injections]
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