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Unify Codomain with a "provided ... in RR" condition #721

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@Rafael-SOWNet

Split out of #596, where @Happypig375 asked: "how to make codomains unified with provided node with the in relation?"

The two look like the same test and are not quite.

  • MathS.Settings.Codomain is a statement about where the function is being read -- real-valued or complex-valued.
  • provided x in RR is a statement about the point.

lim x->0- (x^x) is a limit at a real point of a function that is not real-valued anywhere to the left of it. So the predicate x in RR holds and tells you nothing, while the codomain is what rules the limit out. Unifying them means reading the condition as a claim about the neighbourhood rather than the point -- which is probably what is meant, and is a real change rather than an alias.

Worth doing: a single notion would mean expr provided x in RR and Codomain = RR cannot drift apart, and it would let a domain be stated locally rather than as a global setting. But it is wider than reading MathS.Settings.Codomain in ComputeLimit, which is why the sibling issue does the narrow thing first.

Filed so the question is not lost inside #596.

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