More subtle issue that isn't detected in the symbolic ring
sage: var('None')
None
sage: parent(None)
<type 'NoneType'>
On 10/05/15 22:26, Vincent Delecroix wrote:
> Hello,
>
> What should we do with variable names like 'or', 'and', ... This does
> not break uniformly
>
> The symbolic ring refuses the creation of such variable
> {{{
> sage: SR.var('and')
> Traceback (most recent call last):
> ...
> ValueError: The name "and" is not a valid Python identifier.
> }}}
>
> whereas polynomial rings silently fail
> {{{
> sage: R = PolynomialRing(QQ, ('and', 'or'))
> sage: R.inject_variables()
> Defining and, or
> sage: and
> ...
> SyntaxError: invalid syntax
> sage: 'and' in globals()
> True
> }}}
>
> Vincent
>
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