The function in question is sort-of available as
sage.functions.other.symbolic_limit (which is an inert form, so it requires
a further "simplify").
On Thursday 3 October 2024 at 08:29:50 UTC-7 Nils Bruin wrote:
> On Thursday 3 October 2024 at 04:44:12 UTC-7 Emmanuel Charpentier wrote:
>
> sage: F.limit(X[0]=3) Cell In[9], line 1 F.limit(X[Integer(0)]=Integer(3))
> ^ SyntaxError: expression cannot contain assignment, perhaps you meant
> "=="?
>
> Indeed, the current limit function and method get their arguments
> (variable and value) by analysing a single named argument, whose name must
> be a literal. From limit?? :
>
> The restriction here is python's processing of optional arguments. These
> must have simple names. You can already use
> """
> limit(x0,**{str(X[0]):1})
> """
> now, which isn't beautiful but at least it establishes the function.
> Allowing an explicit dictionary argument would likely open up a whole slew
> of other issues. It looks to me like we're missing a very simple form for
> limit that should be the primitive to all of this:
> limit( f, x, 1)
> i.e.: expression to take limit of, variable with respect to take limit,
> limit value. Then one could just write limit( F, X[0], 0) and one would get
> the default processing of arguments for python for free. We wouldn't rely
> on the programmatic pun of using python identifiers to stand in for our
> symbolic variables.
> Further convenience routines that use syntactic sugar to make things
> resemble more mathematical notation can then be built on top, but at least
> the general primitive is available underneath.
> It may be hard to figure out a way to make such a routine available under
> an easily found name while remaining compatible with what exists now.
>
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